C# Tutorial - Simple Threaded TCP Server - Tech.pro

C# Tutorial - Simple Threaded TCP Server - Tech.Pro

MENU

TUTORIAL LIST

←

Join Tech.Pro Today!

The nerd nerd tab table le is now the cool ta table. ble.

Brandon Ca Cannaday nnaday posted poste d 5 years ago

K

C#

.NET 2.0

BEGINNER

C# Tut Tutor orial ial - Si Si m pl ple e Th Th rea readed ded TC TCP P Se Serv rver er In this tutorial I'm going to show you how to build a threaded tcp server with C#. If you've ever worked with Window's sockets, you know how difficult this can sometimes be. However, thanks to the .NET framework, making one is a lot easier than it used to be. What we'll be building today is a very simple server that accepts client connections and can send and receive data. The server spawns a thread for each client and can, in theory, accept as many connections as you want (althoug (although h in practice this is limited because you can only spawn so many threads before Windows will get upset).

Let's just jump into some code. Below is the basic setup for our TCP server class. using using using using using

System ; System; System. System . Text Text; ; System. System .Net Net. . Sockets Sockets; ; System. System .Threading Threading; ; System. System .Net Net; ;

namespace TCPServerTutorial { class Server { private TcpListener tcpListener; tcpListener ; private Thread Thread listenThread listenThread ;


public Server Server() () { this. this .tcpListener = new TcpListener ( IPAddress . Any Any, , 3000 3000); ); this. this .listenThread = new Thread Thread( ( new ThreadStart ThreadStart( ( ListenForClients )); this. this .listenThread. listenThread .Start Start(); (); } } }

So here's a basic server class - without the guts. We've got a TcpListener TcpListener which which does a good job of wrapping up the underlying socket communication, communication, and a Thread Thread which which will be listening for client connections. You might have noticed the function ListenForClients that is used for our ThreadStart delegate. Let's see what that looks like. private void ListenForClients () { this. this .tcpListener. tcpListener.Start Start(); (); while ( true true) ) { //blocks until a client has connected to the server TcpClient client TcpClient client = this this. .tcpListener. tcpListener. AcceptTcpClient AcceptTcpClient(); (); //create a thread to handle communication //with connected client Thread clientThread Thread clientThread = new Thread Thread( ( new ParameterizedThreadStart ( HandleClientComm )); clientThread . Start Start( ( client );

} }

This function is pretty simple. First it starts our TcpListener and then sits in a loop accepting connections. The call to AcceptTcpClient will block until a client has connected, at which point we fire off a thread to handle communication with our new client. I used a ParameterizedThreadStart delegate so I could pass the TcpClient object returned by the AcceptTcpClient AcceptTcpClient call to our new thread. The function I used for the Parameter ParameterizedThrea izedThreadStart dStart is called HandleClientComm . This function is responsible responsible for reading data from the client. Let's have a look at it. private void HandleClientComm ( object object client client) ) { TcpClient tcpClient TcpClient tcpClient = ( TcpClient TcpClient) ) client ; NetworkStream clientStream NetworkStream clientStream = tcpClient . GetStream (); byte [] message byte[] message = new byte byte[ [4096 4096]; ]; int bytesRead int bytesRead ; while ( true true) ) { bytesRead = 0 ; try


public Server Server() () { this. this .tcpListener = new TcpListener ( IPAddress . Any Any, , 3000 3000); ); this. this .listenThread = new Thread Thread( ( new ThreadStart ThreadStart( ( ListenForClients )); this. this .listenThread. listenThread .Start Start(); (); } } }

So here's a basic server class - without the guts. We've got a TcpListener TcpListener which which does a good job of wrapping up the underlying socket communication, communication, and a Thread Thread which which will be listening for client connections. You might have noticed the function ListenForClients that is used for our ThreadStart delegate. Let's see what that looks like. private void ListenForClients () { this. this .tcpListener. tcpListener.Start Start(); (); while ( true true) ) { //blocks until a client has connected to the server TcpClient client TcpClient client = this this. .tcpListener. tcpListener. AcceptTcpClient AcceptTcpClient(); (); //create a thread to handle communication //with connected client Thread clientThread Thread clientThread = new Thread Thread( ( new ParameterizedThreadStart ( HandleClientComm )); clientThread . Start Start( ( client );

} }

This function is pretty simple. First it starts our TcpListener and then sits in a loop accepting connections. The call to AcceptTcpClient will block until a client has connected, at which point we fire off a thread to handle communication with our new client. I used a ParameterizedThreadStart delegate so I could pass the TcpClient object returned by the AcceptTcpClient AcceptTcpClient call to our new thread. The function I used for the Parameter ParameterizedThrea izedThreadStart dStart is called HandleClientComm . This function is responsible responsible for reading data from the client. Let's have a look at it. private void HandleClientComm ( object object client client) ) { TcpClient tcpClient TcpClient tcpClient = ( TcpClient TcpClient) ) client ; NetworkStream clientStream NetworkStream clientStream = tcpClient . GetStream (); byte [] message byte[] message = new byte byte[ [4096 4096]; ]; int bytesRead int bytesRead ; while ( true true) ) { bytesRead = 0 ; try


{ //blocks until a client sends a message bytesRead = clientStream .Read Read( (message, message , 0 , 4096 4096); );

} catch { //a socket error has occured break; break ; } if (bytesRead == 0 ) { //the client has disconnected from the server break; break ; } //message has successfully been received ASCIIEncoding encoder ASCIIEncoding encoder = new ASCIIEncoding ASCIIEncoding(); (); System. System . Diagnostics Diagnostics. . Debug Debug. . WriteLine WriteLine( (encoder. encoder . GetString GetString( (message, message , 0 , bytesRead )); }

The first thing we need to do is cast client as a TcpClient object since the ParameterizedThread ParameterizedThreadStart Start delegate can only accept object types. Next, we get the NetworkStream NetworkStream from from the TcpClient, which we'll be using to do our reading. After that we simply sit in a while true loop reading information from the client. The Read call will block indefinitely until a message from the client has been received. If you read zero bytes from

the client, you know the client has disconnected. Otherwise, Otherwise, a message has has been successful successfully ly received from the server. In my example code, I simply convert the byte array to a string and push it to the debug console. You will, of course, do something more interesting with the data - I hope. If the socket has an error or the client disconnects, disconne cts, you should call Close on the TcpClient object to free up any resources it was using. Believe it or not, that's pretty much all you need to do to create a threaded server that accepts connections and reads data from clients. However, a server isn't very useful if it can't send data back, so let's look at how to send data to one of our connected clients. NetworkStream clientStream = tcpClient .GetStream NetworkStream clientStream GetStream(); (); ASCIIEncoding encoder ASCIIEncoding encoder = new ASCIIEncoding ASCIIEncoding(); (); byte[] byte [] buffer buffer = encoder . GetBytes ("Hello Client!" ); clientStream . Write Write( ( buffer , 0 , buffer. buffer .Length Length); ); clientStream .Flush Flush(); ();

Do you remembe rememberr the TcpClient object that was returned from the the call AcceptTcpClient? AcceptTcpClient? Well, that's the object we'll be using to send data back to that client. That being said, you'll probably probably want to keep those objects around somewhere in your server. I usually keep a collection of TcpClient objects that I can use later. Sending data to connected clients is very simple. All you have to do is call Write on the the client's NetworkStream object and pass it the byte array you'd like to send. Your TCP server is now finished. The hard part is defining a good protocol to use for sending information between the client and server. Application Application level protocols are generally unique unique for application, so I'm not going to go into any details - you'll just have to invent you're own.


But what use is a server without a client to connect to it? This tutorial is mainly about the server, but here's a quick piece of code that shows you how to set up a basic TCP connection and send it a piece of data. TcpClient client = new TcpClient(); IPEndPoint serverEndPoint = new IPEndPoint (IPAddress.Parse("127.0.0.1"), 3000); client.Connect(serverEndPoint ); NetworkStream clientStream = client.GetStream (); ASCIIEncoding encoder = new ASCIIEncoding (); byte[] buffer = encoder .GetBytes("Hello Server!" ); clientStream .Write(buffer, 0 , buffer.Length); clientStream.Flush();

The first thing we need to do is get the client connected to the server. We use the TcpClient.Connect method to do this. It needs the IPEndPoint of our server to make the connection - in this case I connect it to localhost on port 3000. I then simply send the server the string "Hello Server!". One very important thing to remember is that one write from the client or server does not always equal one read on the receiving end. For instance, your client could send 10 bytes to the server, but the server may not get all 10 bytes the first time it reads. Using TCP, you're pretty much guaranteed to eventually get all 10 bytes, but it might take more than one read. You should keep that in mind when designing your protocol. That's it! Now get out there and clog the tubes with your fancy new C# TCP servers.

Post a Comment

Comments (294) Viswanathct posted 6 years ago I searched a lot for a simple article in tcp reading / writting. After googling with several alternatives i found this page. Simply Good & simple. Thx. An on ymou s 4 years ago


Check MSDN they have a great example. bst78 3 years ago Please show me the microsoft's example. This example is very very good! If you mean the example with server and "dummy" remote server object (http://support.microsoft.com/kb/307445) I can not agree with you :-) An on ymou s 3 years ago Very thnx. Excellent. I learned tcp from here...

view all 4 comments

Mas-Tool posted 6 years ago Yep, it's very simple if you're writing a console application. Try making a chat with with .NET sockets and you'll figure out there are no events support :-/ unlike VB6 with Winsock :) Brandon Cannaday 6 years ago Can you elaborate on the events support? A few years ago a couple of us built a simple chat application using the framework above without any issues. Mas-Tool 6 years ago Hi again :) Well, if you need to make a chat like application you have to use a non-blocking sockets right ? so you use async methods (BeginReceive/EndReceive BeginConnect/EndConnect etc) but the problem is the once you received some data or got connected, you're AsyncCallback is fired and you're on a seperate thread ! so you have to Invoke the mothods for the GUI's thread to know you've received some data :-/ But how can you invoke a method if you're a "pure" class and not a control with a parent control to call the Invoke method? That's the way i see it, but maybe I'm wrong :) I'de like to know what you think! Mas-Tool Brandon Cannaday 6 years ago I don't really like using the Async callbacks so I opted for a blocking socket sitting on its own thread. When a message was received, I would then fire an event out of the "pure" class that can be caught by a higher level control. My event handler would contain the message that was received. The control would then invoke a method to display the message to the GUI. That's the architecture I like to follow, but of course it won't work for every application.

view all 7 comments

Martijn Dwars posted 6 years ago A little parse error in your client program: IPEndPoint serverEndPoint = new IPEndPoint (IPAddress.Parse("127.0.0.1", 3000);

Needs to be:


IPEndPoint serverEndPoint = new IPEndPoint (IPAddress.Parse("127.0.0.1"), 3000);

Brandon Cannaday 6 years ago Good catch. I've corrected the post. suresh kallem one year ago Im new to TCPIP programming, please help me sort out the following problem, i have once server and many clients(around 500 numbers). client system connected to the many hardware devices. server have to monitor client systems status, connected devices and its status and many other operations. here client should send their status to server for every interval of time and server should display it. please suggest me on the same. David posted 6 years ago Very good tutorial. clear and simple. thanks a lot

i Reply An il Ku mar Verm a posted 6 years ago I am searching for windows version of it,it is too simple for beginers

i Reply Some posted 6 years ago Anybody know how to connect via internet? PC1->routerA->internet->routerB->PC2 An on ymou s 3 years ago In this case i expect that you have to make sure that your routers are properly configured. Depending on the type of your router you may have to use the "Port forwarding" of protocol TCP @ your port used by your application. e.g. application uses port 3000 then routerA will need to forward incoming TCP connection on port 3000 to your PC1. Secondary routerB will need to be configured to forward incoming TCP connections on port 3000 to PC2. additionally any firewall has also to be "pinned" @ port 3000 so that your application can talk through the whole "IP-devices-chain" i tried this a few months ago with an cellphone via IP-network to an Windows PC behind NAT and it worked fine about nearly that way. (PC->router->internet->cell-network->cellphone GPRS channel) sevket 6 months ago I want to learn your application. Could you please share your experience with me? Manish posted 6 years ago is there a simple version of this for .net 1.1? specifically with regards to closing the connection releasing client resources to be able to use them again, the next time a connection comes in...

i Reply


Tony posted 6 years ago Is there a particular reason for starting a thread in the constructor? As far as I can tell there would be no difference just calling ListenForClients() and it creates its own threads. Brandon Cannaday 6 years ago ListenForClients is going to block whatever thread calls it while it listens for client connections. Most of the time, my Server class is created on the main thread. I don't usually want to block my main thread while waiting for connections, so I created another thread which can be blocked without affecting the rest of my application. Working Class Hero posted 6 years ago When I close my win forms serverapplication (in debug state) it does not kill that thread. So what should I do? How I kill that clientThread and listenThread? Brandon Cannaday 6 years ago For the clients, you'll want to call Close on their NetworkStreams. This will cause the read to unblock and throw an exception which will be caught by the exception handler (which breaks out of the loop, ending the thread). On the TcpListener, you'll have to call Stop. I'm not sure exactly what this will do to the blocking AcceptTcpClient call. It will either unblock and return null, or it will throw an exception. Either way, you'll want to stick in some error handling. When the error is caught, simply break out of the listen loop. Working Class Hero 6 years ago YES! it worked! yippee thanks a lot! Pc_Madness posted 6 years ago Sorry to be the newb.. but does someone have/know of an example of how to get data to and from the class to a form? :( *sigh* I had an awesome idea for a program, but can't actually make a start on it cos I have to get this TCP stuff out of the way and I have no idea whats going on. :( I miss Winsock.. now that was simple. :) Brandon Cannaday 6 years ago If by "the class" you mean the TCP server class, then it's not too hard. Inside the HandleClientComm thread, fire an event with the data that can be caught by your Form. public delegate void MessageReceivedHandler (string message ); public event MessageReceivedHandler MessageReceived; ... //message has successfully been received ASCIIEncoding encoder = new ASCIIEncoding(); string message = encoder .GetString(message, 0, bytesRead); if(this.MessageReceived != null) this.MessageReceived(message);

Depending on how much information you need, you might want to also pass the TcpClient through your event as well. For a tutorial on custom event handlers, check out this post. Now all you have to do is hook the event from your form.


Server server = new Server(); server.MessageReceived += new MessageReceivedHandler ( Message_Received ); void Message_Received(string message ) { //update the display using invoke }

Since the events are fired on the server thread, you can't update the form directly - because you can't modify UI elements on threads that didn't create them. You'll have to use Invoke, which executes code on the UI element's thread. For some more information on invoking, I would recommend this article. I hope this helps. Pc_Madness 6 years ago woot, thanks Reddest. :) An on ymou s 3 years ago thnx Sir. I like it

view all 8 comments

Chris Surfl eet posted 6 years ago OK, I think I must be missing something here. I keep getting an error stating "You must call the start method before calling this method" on the TcpClient client = this.tcpListener.AcceptTcpClient() line. I've definately started the server, any ideas what this could be? Thanks a lot! Brandon Cannaday 6 years ago That error is a result of not calling tcpListener.Start() before the call to AcceptTcpClient(). If you're saying you definitely called it, then I don't have any other ideas. I'd double to check to make sure you absolutely called tcpListener.Start(). Chris Surfl eet 6 years ago Hmm got a little further. The problem is to do with closing the server down. I can send data to it without error the first time, (creating the server object and sending the data from the same test case method) but next time I run the code I get a "Only one usage of each socket address (protocol/network address/port) is normally permitted" exception. I added a method to my server called Close that simply calls Abort on the listen thread and Stop on the TcpListener. If I call this after closing my request stream I get an IO exception while writing to the stream, above the point where I call the close method?? Really confused haha Brandon Cannaday 6 years ago Calling Abort is never a good way to close your threads - and it's not actually a guarantee that the thread will terminate. Calling Stop() on your TCPListener should unblock your listen thread and throw an exception - which you should catch and return out of your function (which will end the thread). Your first error is caused by calling Start() while another application is listening on that port. Typically,


you can't have two TCP servers listening on the same port. Either your TcpListener was still running when you launched the application again, or you have another piece of software on your computer using that port.

view all 6 comments

JS posted 6 years ago Excellent tutorial! Thanks a lot!

i Reply Vishav Bandhu Sood posted 6 years ago when i got connected to the various clients in tcp listner(server)suppose initially if there are 1000 clients connected but after some time it shows only 500 or 400 clients connected.actually clients are connected but server is not responding prooerly,but after stopping server it agains shows the actual no of the clients connected.(i thinks this problem is related to server port buffer size)plz help .....

i Reply Simnesh posted 6 years ago Hi, i want to send data from a client to another client through server... please help me Brandon Cannaday 6 years ago How to do this depends a lot on the application you're trying to make, your protocol, and your server architecture. Here's an example scenario that might get you started. When a new client is connected, you could assign them a unique id, or they could actually send you the id (a username or email address). This id would then be sent from another client in a request to forward the information. This would mean your protocol would have to include the id of the client the other client wants to send data to. On the server, you'd simply read the message, get the id of the client to forward the message to, iterate through your clients to find the recipient, then send the data. Simnesh 6 years ago Hi Is it possible to send a class object from a TcpClient to TcpListener... I want to send an object of a class or an array of string to the TcpListener Brandon Cannaday 6 years ago It sounds like remoting is what you might want here, but it can also be done using TCPClient and TCPServer. The send an object, you'll first need to serialize it to a byte array. Then, on the receiving end, deserialize the object back into the desired object. Here's a tutorial I found on the web explaining how to do this: Object Serialization and Deserialization in C#. Nigel Bogle posted 6 years ago I have an application which is essentially a TCP/IP Server to which up to 16 clients can connect at any one


time each on it's own unique port, i.e. 4001 - 4016. The connections establish ok but after a period of time the connections seem to disconnect and I'm not sure why. when you run NETSTAT from the DOS Prompt it shows the connections in a CLOSE_WAIT state. The clients then have to reconnect... and so the loop goes on... Whe I try to write back to the client and it is disconnected I get an error code of 10053 which means that the software in the host machine has disconnected or something along those lines. Has anyone else had experience of this? Could it be a timeout? How can I ensure that once my server accepts a client connection that it helps to maintain the established connection? Any and all help appreciated. Nigel.

i Reply Dvaz posted 6 years ago Thanks for the nice tutorial, just found it today. Is there a way to start the server in its our thread at start? The reason i ask is because the user on my UI needs to click a button to start listening, but by doing so, it blocks my main UI. Thanks! Brandon Cannaday 6 years ago The server in this tutorial is created in its own thread. The constructor of the Server class creates the thread and begins the listening process. All you'd have to do is not call this.listenThread.Start() until the user clicks the button. Dvaz 6 years ago Ahh, i see. I used a background worker to call the listen call and it also worked, will try the other. One more thing, i am trying to pass a connected / disconnected status to the mainform as wel as the number for files received, any easy way to do that? So far im using you event example to send the message back but what are the procedures if i want to send more data back to my MainForm? -Thanks! Tagnard posted 5 years ago Hi. i am trying to get the client to read what the server sends but i am new to this. Can you tell me what i am doing wrong? http://tagnard.net/2008/06/09/c-serverclient/

i Reply Eric posted 5 years ago Thanks for the nice tutorial. I tried it (ported to C++) and it works fine. Still, when exiting the main application I can't find a way to stop a clientThread when there is an active connection. I mean I can use tcpListener.Stop(), what causes a SocketException that unblocks AcceptTcpClient()in the ListenForClients thread, then I use break to exit the loop and this thread. But if a client is actually connected, corresponding HandleClientComm thread remains stuck waiting for something to be read. So far, I haven't found any clean way to gracefully close the socket and to exit this thread. I don't see how to close the NetworkStreams (as proposed in an earlier comment.) from the outside of the


client thread. And from the inside, well the read is blocking, so... Any idea ?... Thanks, Eric Brandon Cannaday 5 years ago I usually create an object for clients. The thread would be located inside the client object. The server would just keep a list of clients and whenever you stop the server, you'd loop through each client and call a stop function on them, which calls Close on their NetworkStreams. You can modify the above code to do something similar by keeping a List of just the NetworkStreams. Whenever a new client is connected, add the NetworkStream from HandleClientComm. Whenever a client is disconnected, remove the NetworkStream from the list. Eric 5 years ago thanks for the suggestion, it made it. Johan posted 5 years ago Hi, have a strange problem... the tcp server connects fine with clients on the local network but 'kind of' connect with client comming from the Internet... it always wait about 16 - 20 seconds to connect, but then the remote client seems not to realize this... (also tcp port monitors show the incomming connection connecting almost immediately, but somehow not telling the server) please help...

i Reply Nicholas posted 5 years ago Hi, i have an error message "A blocking operation was interrupted by a call to WSACancelBlockingCall" when set tcplistner.stop(), how to solve it ? thank you Eric 5 years ago this is normal behavior when interrupting a blocking socket (i.e. waiting for clients). WSACancelBlockingCall is called and a SocketException is thrown (see my post above). Just catch this exception and use it to exit the thread ('break' in the infinite while loop). Vitalij posted 5 years ago Hi! If it's possible, send me an initial code of this program. Please!

i Reply Jason posted 5 years ago Nice.. Easy to use and build on..

i Reply Saga posted 5 years ago Hi, Since i m very beginner in C# coding for TCP/IP server.. I can get the concept and working of the code through ur explanation and questions but i cant do it practically./. Can u please explain that with a visual mode or the screen shots of wat to do? Please help me bro.. I m in need of it.. I will b very grateful for the help ... Saga 5 years ago


ya its me again Saga.. Can u please mail me the one wich i asked in the previous thread... My mail id: [email protected] Opariti posted 5 years ago This is a great article; who explains clearly is really someone who really knows! I didn't give it a try yet but from the beginning it points to the TCPListener application blocking issue. I'll bring it into a chat-type application (client-server however) between two programs running on the same machine or remotely (first both on 'localhost'). I understand that threading the server separates it from the main program thread and avoid blocking all while in the listen loop. After acknowledging all that, just a stupid question (sorry I'm new to programming...): would it be possible that I make ListenForClients a method (rather than a class) of my main thread (since I want to quickly send and read messages from/into the main thread through your TCP server)? Many thanks!

i Reply Bryan posted 5 years ago Hey, not much to add. Just wanted to say great thread. EXCATLY what i've been looking for. THANKS!!!

i Reply Serhat posted 5 years ago Thanks

i Reply Shinoj K posted 5 years ago Hi, i am in a big trouble to fix this problem.... can any one suggest me a control, which can display animated gif images and text.... this is for a chat application....

i Reply Kristian posted 5 years ago Ok... so I got the client-server part done quite easily... What I want to do now is to have two way async communication using this only connection. Is that possible or do I have to have two connections, one for reading and one for writing, on different ports? Any other way you can suggest?

i Reply Joap posted 5 years ago I have a very weird problem here. When I copy and paste the client into visual C# studio 2008, it doest recognise the .Connect method of a TcpClient. Please help me! Thanks.


i Reply Shinoj K posted 5 years ago Hi, I have develeped webcam view in my chat.In that only one client can view webcam at time.I want to do view more than one client at time(web cam sharing).I am using TcpListner and TcpClient.Can Anyone Help Plz.Urgent.Thanks In Advance.

i Reply Sami posted 5 years ago thank you

i Reply Jeff posted 5 years ago Gonna try yours. Too soon to tell, but no crashes so far (like mine). One issue I have always had with the GPS via GPRS devices we track: they will un-gracefully disconnect when they switch cell towers, then reconnect. So eventually, there's lots of dead connections that are not recylced. I tried making a collection and saving each client object as it's created. The idea was to purge the clients, but I am not sure how: TcpClient client = this.tcpListener .AcceptTcpClient(); clientArrayList.Add(client);

...so now I have the client objects in my collection. But I get errors when I try to delete them like this: foreach (TcpClient c in clientArrayList) { c.Client.Close(); }

So I guess I am still looking for a way to recycle these old connections. Suggestions appreciated.

i Reply Ken posted 5 years ago I would like to say thanks. The main article is detailed and straight forward but the additional information in the comments has also been very helpful.

i Reply Kemp posted 5 years ago very simple as well useful beginner like me,,,,,,,.

i Reply Martin posted 5 years ago Anybody, have you had any issues with a (C#) socket exiting into a CLOSE_WAIT therefore not allowing to use the


same address/port.? I am closing the connection at both ends and still get the CLOSE_WAIT (not all the time). I used extensively C/C++ berkley socket and I never got the problem. Anybody? An on ymou s 4 years ago a CLOSE_WAIT usually indicates a problem in the app (server), probably from not closing the socket. You need to catch when the client closes (or times out/drops off/whatever) and close on the server side. You should see TIME_WAIT (ok), but CLOSE_WAIT is usually not good sign. An on ymou s posted 5 years ago Good article, hope you will keep up ,creating more of it, in the same simplify style, someday. :) Thx!

i Reply Guilherme posted 5 years ago Good article!!! Procurei por um assim a temposs.. muito bom msm ... parabéns!!

i Reply Ron posted 5 years ago Excellent tutorial and very useful from both clarification and simplification perspectives. Just one thing: shouldn't clientStream.Close() be called prior to tcpClient.Close() in HandleClientComm? Otherwise, won't the network stream remain open (unless if that was by design/intention, although I don't see why, and how, one could recover the same stream for future use after closing the TcpClient)? Thanks again and great work!

i Reply Leslie posted 5 years ago Awesome tutorial. Thanks Reddest.

i Reply Robert posted 5 years ago I am new in this tcp programing and just have question: I have created the TCPServer.dll and tcpClient.exe, how to test thme? Robert 5 years ago Sorry give the confuse, and question is simple: How to start TCPServer? Brandon Cannaday 5 years ago In my example code the server is started automatically upon construction. Johnny posted 5 years ago Hi there Reddest, I am developing a MUD (multi user domain) in C# and i wanted to ask a question:


What i need is an application just like this, but i want the ability to have events driven by commands texted into the MUD, i’m sure you may be familiar with old school MUDs, if not its a text based D + D type adventure game, supporting multiple users that can interact. There will be chatting of course, but mainly each user will have commands and need series of data stored (in class objects i’m certain) ANYWAY, What i need is to know if this threading business will affect each user? Like if i’m player Johnny and johnny does this or that in the game, how will other players in the room be made aware? IS this the wrong type of server for my needs? Thanks!

i Reply Christiaan posted 5 years ago Exactly what I was looking for \^\^

i Reply Jester posted 5 years ago Forgive me if this has already been answered, but I didn’t see it. Is there a way to send the chat messages the server receives to all the connected clients?

i Reply Razvan posted 5 years ago Great code…simple and stable; If you want to test your tcp server with simulated clients, you can use ‘telnet’ to achieve this. Open a command prompt window in XP or Vista. Type the following command: telnet host port where host=local computer name, ip address(127.0.0.1 will always be your own computer) or domain name that identifies the computer on the internet. port = port number the TCP server is supposed to listen to If you have a successfull connection then a black screen with a blinking cursor should appear. If you open more command windows and issue the same command you will simulate multiple clients connected to the server. Closing that command windows should disconnect that client. Cheers, Razvan 5 years ago Forgot to mention: sending information to your server using telnet and beeing able to parse it is not possible unless your TCP server uses VT100 Application layer protocol, which an end programmer has to manually implement it.Though i strongly discourage to do that. You can use telnet to test server shutdown, while clients are connected and beeing able to easily troubleshoot exceptions, manage server resources when clients connect/disconnect and even troubleshoot timeout disconnect methods if you clients are connected, but donn’t send anything over a period of time.This is very a server memory friendly approach since a real server needs to handle thousands of simultaneous connections at a given time. An on ymou s posted 5 years ago


I can get the server to send information to the client, but its a blocking call. How do you make the client listen for incoming data from the server and keep the GUI alive at the same time? Thanks in advance.

i Reply Emil Haukeland posted 5 years ago Your tutorial was a great way to get starting on networking in C#. You are very good at explaining this hows og whys :) Thanks a bunch!

i Reply Wildhorn posted 5 years ago Man I registed JUST to tell you how amazing this tutorial is and how good you are at explaining stuff. I browsed I dont know how many tutorial about this without understand shit, but with you it was so simple, easy and amazing... /bow You are my new god! :)

i Reply Brad Modenfield posted 5 years ago Hi thanks for good tutorials. I have a serious problem. I want to develope an "server" that can recieve streaming data from sensors (the number of could be variated), Then the data should be pushed after it has been "modified" a bit, into the database (SQL Server). I dont know where to start, im aware that it may will need some kind of a server and it looks like that i also need threads and async communication. But how can i recieve stream data directly with TCP?

i Reply hariom posted 5 years ago hi thanks for gud concepts.. but iam confused at Async ..

i Reply Michael posted 5 years ago Worked the first time I used it. Many thanks, you saved my bacon...

i Reply mahmoud posted 5 years ago greate explanation

i Reply


mahmoud posted 5 years ago but i think we will find "out of memory Exception" when alot of clients conected as we creare aseparate thread for Each client so these no of threads will lead to that exception

i Reply littleman posted 5 years ago Hi thanks, for the great tutorial, BUT the NetworkStream.Read() command seems to work only the first time. I copied your code exactly (!), compiled and started the server. When I connect via telnet 127.0.0.1 3000 (or any other client) I can just send the first time. The second time NetworkStream.Read throws following Exeption.Message: "The argument is out of range of valid values! Parameter: size ... Do you have any suggestions? Cheers, littleman littleman 5 years ago solved .... :) Brandon Cannaday 5 years ago What was the issue? An on 999 3 years ago Yes, please do tell us the solution, I am experiencing the exact same thing... Muhammad A rshad posted 5 years ago Hi, Every one i have a card reader secrutiy device of pegasus brand, which is connected on port 4001 , i want to read and wirite data on this device any one help me please, while i am using Visual studio 2008 C# code

i Reply Ohad posted 5 years ago Hi Reddest, great tutorial and code! I was wondering what a realistic number of concurrently connected clients (=\~ threads in this case) would be in this implementation, on a standard modern PC using winXP SP3 and VS 2008 / .NET 3.5 SP1 I realize this may depend on many factors, but a rough estimate would be great - dozens of clients? hundreds? thousands? Much appreciated, Ohad

i Reply Jon Hunter posted 4 years ago Great article. Well written and easy to understand. I wish all articles were like this one !

i Reply An on ymou s posted 4 years ago


Great article. One question though. Since the AcceptConection is blocking on the thread, How can I gracefully end everything when the Server, in my case a form, closes? Brandon Cannaday 4 years ago When TCPListener.Stop() is called, it will unblock with an exception. Simply catch the exception and break out of the loop. An on ymou s 4 years ago that is what I was doing, just wanted to see if there was some other way that did not raise an exception. Brandon Cannaday 4 years ago You can probably get around it using BeginAcceptTcpClient and EndAcceptTcpClient. tohox posted 4 years ago Hi, I've implemented your server solution and it works fine except that threads seem to be accumulating and not being released as the clients close their connection. Everytime a connection is caught by the TcpListener the size of the application in memory grows by a few kB but upon the final tcpClient.Close() in the HandleClientComm the ressources don't seem to released. So my application is constantly inflating... It was my understanding that once the connection was closed the thread would simply vanish? thanks! An on ymou s 4 years ago Hi again its tohox, So I did my homework thoroughly debugging my app, reading many things about threading and .Net memory management and it appears that this memory inflation is somewhat normal given the way managed code works and how the garbage collector handles ressources. When hitting the server with many requests per second the memory usage quickly grows to a few MBs more than when the server was first started and it then tends to stabilize. After that it will occasionnaly grow or shrink but stays roughly the same. Forcing the garbage collector to do its job will momentarily free up a few kilobytes but memory usage will eventually crawl back up... So, false alarm and many thanks for a great tutorial! An on ymou s posted 4 years ago Thank you for the article. This is the first piece i've seen on tcp communication in c# .net. I have a question for you though. Is it common practice to use a blocking loop to wait for client connections? It seems a bit like a duct tape solution to me. Are there no .Listen() methods or anything of that nature? Would a .Listen() method simply wrap a blocking loop? Just seems... i don't know... inelegant? Thank you again though. Great article. :) Brandon Cannaday 4 years ago I like to use the blocking call myself, but there are asynchronous methods that won't require it. Check out BeginAcceptTcpClient and EndAcceptTcpClient. Rehab posted 4 years ago thanks for this good article so much really i have searched a lot but this was the best i have a silly question as i am new to network programing what happen if the accept client has no object to return??


private void ListenForClients () { this.tcpListener .Start(); while (true) { //blocks until a client has connected to the server TcpClient client = this.tcpListener.AcceptTcpClient(); //create a thread to handle communication //with connected client Thread clientThread = new Thread(new ParameterizedThreadStart (HandleClientComm)); clientThread .Start(client);

} }

An on ymou s 4 years ago run your program and place breakpoints at the accept client line and one at the line just after that, you will see that the accept client will not move to the next code line untill a client is connected so the object will not be nothing An on ymou s posted 4 years ago Great article, but how can I use this one when I want to connect to a remote computer on Internet with a router(a local ip adress) Brandon Cannaday 4 years ago In this example, the TCP server is listening on port 3000. The router would have to be configured to forward that port to your desired computer. suchislife801 posted 4 years ago What a clean and great sample you've posted. I was just wondering one thing. Would you be so kind to perhaps post the following code updates if its not to complicated: Everytime the server accepts a client, this client is added to a list. Everytime a message is sent to the server, a true or false flag is sent as well telling the server to broadcast the message back to the client who sent it or to all clients on the list of connected clients.

i Reply An on ymou s posted 4 years ago Great article, thanks for posting this. I have a problem though... It seems that the server can only be connected to using a client on the same computer as the server or on the same network (intranet). How do I open the server up to connections from the open internet? Thanks in advance to anyone who can help me with this issue! An on ymou s 4 years ago Here is my code: using System;


using using using using using using

System.Collections.Generic; System.Linq; System.Text; System.Net.Sockets; System.Threading; System.Net;

namespace SimpleConsoleServer { class Program { // Global methods private static TcpListener tcpListener; private static Thread listenThread ; private string endl = "\r\n";

///
/// Main server method ///
static void Main(string[] args) { tcpListener = new TcpListener(IPAddress.Any, 80); listenThread = new Thread(new ThreadStart(ListenForClients )); listenThread .Start(); } ///
/// Listens for client connections ///
private static void ListenForClients () { tcpListener.Start();

An on ymou s 4 years ago Follow-up: I resolved the issue. Apparently the corporate domain my computer was joined to had settings which blocked all ports for incoming requests not on the domain. ash1988 posted 4 years ago Hi I've been trying to piece together some code from this tutorial for my application and have come across a few problems. Can anyone help me out with seeing why I can't send more than one message in either direction with the code I have, and why this would be the case. I get the feeling I've done something seriously wrong! Thanks for any help. Server Side using using using using using

System; System.Collections.Generic; System.ComponentModel ; System.Data; System.Drawing;


using System.Text; using System.Windows.Forms; using using using using

System.Linq; System.Net.Sockets; System.Threading; System.Net;

namespace TcpTrainServer { public partial class Form1 : Form { private static TcpListener tcpListener; private static Thread listenThread ; static NetworkStream clientStream ; static string textFromClient = ""; //private string endl = "\r\n"; public delegate void MessageReceivedHandler (string message ); public event MessageReceivedHandler MessageReceived ; public Form1() { InitializeComponent(); initiateListen (); }

Brandon Cannaday 4 years ago My only guess is that clientStream.DataAvailable is returning false. DataAvailable only returns true if data is available to be read. Since you're reading all of the data from the stream in the loop, it will most likely revert to false by the time the loop ends. ash1988 posted 4 years ago ok so with that aside, am I right in my understanding that once a "clienstream" has been established between server-client that they can send/receieve using this without any issues with blocking sockets or anything like that? In your example you have this code to send from server-client NetworkStream clientStream = tcpClient.GetStream(); ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder.GetBytes("Hello Client!"); clientStream.Write(buffer, 0 , buffer.Length); clientStream.Flush(); Was I correct in adding a handlecomm method at the client end because how else would the application know how to handle the receival of data? Im confused in regards to the part where say I go to send a message from client-server, how is it that only the server "handlecomm" and not the client "handlecomm" won't see data in the stream to be read ? Thanks

i Reply


ash1988 posted 4 years ago disregard my last message, I got it working, you were right about the DataAvailable returning false. I've just placed an infinte true loop around the other loop, not sure if thats the best way to get around it but its working!! Thanks heaps Brandon Cannaday 4 years ago You could just replace the inner loop with a while(true) loop. On error conditions you call break, which will correctly exit the loop. If you surround the inner loop with another one, you might have problems getting that thread (and your application) to exit. Teres posted 4 years ago I have modified a bit client and server, so that server replies to client and they communicate until client types "exit". CLIENT Console.WriteLine("Type 'exit' to exit" ); while (true) { Console.ForegroundColor = ConsoleColor .Green; Console.Write("SEND: "); buffer = encoder .GetBytes (Console.ReadLine ()); if (encoder.GetString(buffer) == "exit") { break; } Console.ForegroundColor = ConsoleColor .Green; Console.WriteLine("SENDING: " + encoder .GetString(buffer)); clientStream .Write(buffer, 0, buffer.Length); Console.ForegroundColor = ConsoleColor.Red; clientStream .Read(buffer, 0, buffer.Length); Console.WriteLine("REPLY: " + encoder .GetString(buffer)); }

SERVER: while (true) {

bytesRead = 0; try {

//blocks until a client sends a message bytesRead = clientStream .Read(message, 0, 4096); } catch { //a socket error has occured break; } if (bytesRead == 0) { //the client has disconnected from the server break;


} //message has successfully been received Console.WriteLine("RECEIVED: " + encoder .GetString(message, 0, bytesRead )); //REPLY /*sMessage = encoder.GetString(message, 0, bytesRead); sMessage = sMessage.ToUpper(); Console.WriteLine("REPLY: " + sMessage); message = encoder.GetBytes(sMessage); Console.WriteLine("REPLY: " + encoder.GetString(message, 0, bytesRead)); clientStream.Write(message, 0, bytesRead);*/

/*message = encoder.GetBytes(encoder.GetString(message,0,bytesRead).ToUpper()); " "

Can you tell me why only the last "method" in server works ? If I try to do the same thing with two previous "methods", after receiving first message from client and sending it back, server shows that client has disconnected. On the other hand those two "methods" work fine if I don't try to do anything with buffer (just send it back). Teres 4 years ago Why can't I use the same buffer I received message to ? Teddy posted 4 years ago I need help urgently. An application written in C++ writes messages in the form of (char*) struct continuously. I need to create a windows server ( written in c#) that would receive that message from that socket and parse that and send the information back again in the same socket. Please help me 1. how the c++ message will be read by c# codes? 2. How the threading model would be for the c# application? 3.How it will write data into socket that would be readable by c++ application? PLeeeeeASE HELP. An on ymou s 4 years ago C# will have no problem receiving CPP char*s (they point to char[]) and CPP will have no problem receiving C# char[]s, it depends on your methods for retrieving data. Perhaps something more "beginnerish" would be beneficial before tackling threading and sockets.. the person with the toothpaste tube posted 4 years ago excellent tutorial

i Reply the person with the toothpaste tube posted 4 years ago Console.WriteLine("Thank you for the tutorial." );

Shankar S 4 years ago is there any way to test the connectivity(telnet or ping) using C# .net if we enter the source(usually not


the machine logged in) ip port and destination ip port in a simple form? Thanks in Advance. An on ymou s one year ago Agreed sonea posted 4 years ago Hello. Need your help! In the article you've said that you usually save collection of TCPClient. Is there any way to detect the client is discinnecting? Thanks for any advices! Brandon Cannaday 4 years ago Yes, clientStream.Read(message, 0, 4096), will throw an exception (probably IOException), which indicates the underlying socket has been closed. sonea 4 years ago Thanks a lot! I'll try this. An no ni mo us posted 4 years ago Hello, how do you stop the server? I mean, your Read call has Infinite timeout so the call will block forever. Then, how do you can stop the server if you need to?

i Reply An on ymou s posted 4 years ago This stuff looks interesting although I can't seem to get any of the examples to compile in Visual Studio 2005. Can anyone post a complete compileable example of the client and server app where data communicated between the client and server is displayed in a form control?

i Reply kami posted 4 years ago Hello everyone, I am new in Socket programming, I want to send file in chunks from server to client side. As server send packet(packetID + SizeofPacket + Data) to client side, Client save the data in buffer and send the response(packetID) back to server. then server looks the packetID and send the datachunk related to packetid. Can I achieve this by using TCP sockets. Can someone explain me how. Thanks

i Reply webmartians posted 4 years ago Curiosity: the example starts a thread to handle the communications and provide the "intelligence" (HandleClientComm). What about using AcceptTcpClient

(which blocks until a connection is available) - acquiring the entire message - and then spawning a thread to provide the process? Yes, the acquisition of the message is then in-line, but, if I read my TCP specs


correctly, it will always be in-line because of the buffers. For example: using using using using using using

System; System.Diagnostics; System.Net; System.Net.Sockets; System.Text; System.Threading;

... TcpListener lr /*Listener*/ = new TcpListener(IPAddress.Parse(InternetProtocolAddress), InternetProtoc olPort); for (lr.Start(); MyListenerIsNotShutDown );) { TcpClient cl /*Client*/ = lr.AcceptTcpClient (); byte[] bf /*Buffer*/ = new byte[8192]; string mg /*Message*/ = string.Empty; NetworkStream sm /*Stream*/ = cl.GetStream(); for (int ct = sm.Read(bf, 0, bf .Length - 1); 0 < ct; ct = sm.Read(bf, 0, bf.Length - 1)) mg += Encoding.ASCII.GetString(bf, 0, ct ); mg = mg.Trim(); try { // Start a new thread to process this message. Thread thd /*Thread*/ = new Thread(new ParameterizedThreadStart (MyMessageProcessor )); thd.Start(mg); } #pragma warning disable 168 catch (OutOfMemoryException ex /*Exception*/) { // There is not enough memory to start the thread: do it in-line, thereby, throttling response s. MyMessageProcessor (mg); } #pragma warning restore 168

... public static void MyMessageProcessor (object prmMsg)

... Just to add to the confusion, the send is therefore stateless: TcpClient cl /*Client*/ = new TcpClient(); cl.Connect(new IPEndPoint (IPAddress .Parse(prmAdr), prmPrt)); ASCIIEncoding ec /*Text Encoder*/ = new ASCIIEncoding(); byte[] bf /*Buffer*/ = ec.GetBytes(prmMsg); NetworkStream sm /*Stream*/ = cl.GetStream(); sm.Write(bf, 0, bf.Length); sm.Flush();

webmartians 4 years ago Never mind... Don't do it (spawn the thread AFTER acquiring the text)... The newer Windows TCP


stacks do indeed provide for multiple, concurrent connections' queues being drained. khan posted 4 years ago Hello, is it possible that 2 clients connected to same server can communicate each other using c# multithreading programming?? Thanks... I need help webmartians 4 years ago The server merely receives and replies to clients; client to client communications are not possible ... strictly speaking. I suppose you could write your server's message handler to recognize some kind of forwarding command prefix in the message (eg: "To 12.34.56.78:50000"). The sending client would have to put that it its message. However, that brings up the question, "If the client knows the IP address and port of the other client, why is it not sending the message directly?" khan posted 4 years ago Hi, I am writing Bluetooth simulation program in c#. I am writing two clients as Master and Slave device. and one server application which act as a channel between Master and Slav device. so, Master communicate with Slave through Channel. Later I will add interference at channel application and see the effects on Master and Slave, as these Master sending a big file in chunks to Slave. Please I need your's suggestions, how I achieve this??? Thanks Khan

i Reply mrRumble posted 4 years ago hii, how to receive and send data to linux client from .NET using format struct tcpdata { unsigned long code; unsigned char msg[256]; } thanks,

i Reply webmartians posted 4 years ago I got most of this working ... in a "harsh" environment (slow processors at both ends, zilch memory). Here is what I learned: 1- recv returns zero when its current crop of buffers for the connection are empty. THAT DOES NOT MEAN THE MESSAGE IS FULLY ACQUIRED! Maybe everybody else got this; I didn't and had to add an endianindependent, length field at the beginning of each message. 1b- mrRumble - "On the nose!" (length field at the beginning of each message) ... except that there are a number of machines of different "endianness" that do not store the bytes of an unsigned long in the expected order (assuming you want to talk to not just C# nodes). You must replace that unsigned long (or long) with four, distinct byte values, where you know that the first one is the high-order, and so on (or whatever order you want, as long as it's consistent). 2- When the client (sending) side is C# and the server (receiving) side is C/C++, when the C# closesocket executes, unread data at the server (C/C++) side (or, maybe, still in flight) is destroyed ... sometimes ... often enough to be catastrophic. Strangely enough, this does not seem to happen in reverse (C/C++ client sending to a C# server). I found two WWW reports of similar behavior - "fire and forget" is not a good philosophy, here. The answer is to require some kind of acknowledgment for every transmission (for example, an empty message) before the sender executes closesocket. 3- The idea of the loop around the server's loop is a real frustration-preventer: having the code able to say,


"This failure is too nasty for me to handle in the inner loop; I'll reset and restart everything!" definitely makes unit testing more pleasant. I suggest a Sleep of a good second or so at the end of the outer loop: if (this is not a shutdown) Sleep(1000);

to give the system some cycles to tidy whatever messes it needs to clean up and, maybe, restore resources that will allow the next, major cycle of your server to execute successfully. 4- Consider UDP instead of TCP. If you can do what you need to do in UDP, use it instead of TCP. Remember, UDP blasts your packets all over the place: they WILL arrive out of order. You'll need, instead of just a length field, a (packetN)/(ofMpackets) field in each transmission. ...but UDP is much faster, simpler, and, oddly enough, can end up being more robust than TCP. Hard to swallow, I know, but that has been our experience: UDP gets more data through bad pipes than TCP does. ...hope this saves somebody some grief...

i Reply milop posted 4 years ago If each thread is communicating through the same port, how is it that one client doesn't get the data intended for a different client? Does the NetworkStream object create the "isolation"? Brandon Cannaday 4 years ago When a connection is made, a socket will be formed between the server and the client. Each port can have several active sockets. The .NET framework and the OS maintain this information. http://www.freesoft.org/CIE/Course/Section4/6.htm http://en.wikipedia.org/wiki/Internet_socket milop 4 years ago Thanks. After a bit of a brush up on sockets I confirmed this with NETSTAT. I have one more question, if you don't mind. In your article you stated that you like to keep the "client" object around. How would you know that a "client" object can be reused? The "Connected" property? Thanks again. Brandon Cannaday 4 years ago I've never reused a TcpClient object. In the example code, the client only lives in the scope of its thread. There's no way for the server to find a client when it's needed. What I meant by "keep it around" was to put it in some sort of collection so the server can look up a client when it needs to send it something. pollardomax posted 4 years ago Thanks the tutorial is great, I've got it working... I would need to send data from the server to all the connected clients.. is there any simple way to do this in your example?

i Reply goldenfox posted 4 years ago @The Reddest: Can you give me an idea on how to use this method to allow the server to send data(possible huge data) to coming from mysql to the clients connected to it? I would like to use this technique to create something like a middleware between clients and mysql server.


Thanks, goldenfox

i Reply Al iB aba posted 4 years ago When My code is in clientStream.Read(...) loop and how can I break it? Can I set a ReadTimeout such as SerialPort.ReadTimeout? Thanks

i Reply topagent006 posted 4 years ago what is the maximum connection can I have using this chat method? Is it limited by the OS in term of threads it can have? What could be other limitations? Thanks Brandon Cannaday 4 years ago There's basically no limit outside of your computer's resources. Memory, threads, and available handles. A normal desktop should be able to handle a least a thousand. topagent006 4 years ago Wow. Thank you for your prompt reply. ravik posted 4 years ago Hi , Thanks for posting the tutorial. I need some information for sending and receiving messages through telnet using tcp connection after the connection and the valiadation of the login string.and the data will be storing in the log file and the listbox in mainform. can anybody help me how can i solve this issue.

i Reply samad posted 4 years ago Hi, you put great stuff on this page... as i can see in above example using TCP .. Does TCP client create one seperate thread on TCP listener server and thumb of rule there shouldnt be processor*2>running thread on server side.. i saw some articles where they explain select and pooling technique for nonblocking server...and they used socket class rather thn TCP i am trying to implement one server which can serve thousands of clients ... do you have any good example or article regarding that Thanks in Advance

i Reply lo u posted 4 years ago Hi,thanx for your good tutorial. here is question as Nigel asked it long ago. i have the same problem.and i could not fine the answer,can any


body help me. I have an application which is essentially a TCP/IP Server to which up to 16 clients can connect at any one time each on it's own unique port, i.e. 4001 - 4016. The connections establish ok but after a period of time the connections seem to disconnect and I'm not sure why. when you run NETSTAT from the DOS Prompt it shows the connections in a CLOSE_WAIT state. The clients then have to reconnect... and so the loop goes on... Whe I try to write back to the client and it is disconnected I get an error code of 10053 which means that the software in the host machine has disconnected or something along those lines. Has anyone else had experience of this? Could it be a timeout? How can I ensure that once my server accepts a client connection that it helps to maintain the established connection? Any and all help appreciated. Nigel. Brandon Cannaday 4 years ago I don't know what could be causing it, and it's something I've not experienced. I checked the documentation for TcpListener and TcpClient, and their timeouts are all initialized to infinite. Bubba posted 4 years ago This is a really great example and I have a working implementation. Thanks. One thing I can't seem to wrap my head around though. In the scenario you have covered, a client sends a message to the server and the server responds. How do you set up for a scenario where the server can also send a notification to the client. The client would always have to be in a listening state (ie: bytesRead = clientStream.Read(message, 0, 4096); ) which would cause issues when the client sends a command and is waiting for a response from the server. Would I need two connections to handle this or is there a more elegant way to accomplish this ? Brandon Cannaday 4 years ago If the client sends a request and is waiting on a response, there's no guarantee that the notification won't be received before the response. This scenario should be handled in whatever protocol you've designed for communication. Typically people reserve the first few bytes for the type of message being transferred. So if the client is waiting for a response of type n, and receives a different message type, it can process the notification and continue waiting for the message. lo u posted 4 years ago Thank you very much.

i Reply lo u posted 4 years ago void main (Hi...arg,events,help) { i want to save tcpclient in a collection i used Hashtable and then use an array of TcpClient but when server want to send data t specific client with specific ConnectID it say that can not use dispose object it means that the tcpclient that i saved in server is disconnected.client.(connected==false) i think my previouse problem has the same source as this is. so if im am wrong in saving client how should i do that.and be able to send info from server to specific client. [edit post] after i post this i found that the thread that this client has run on it(also other client on their own thread) is stoped.and i think this is the source of error 10053 software in you host disconnect you.(sth like that).but i


dont know why the threds stop afterward.and i also geuss it might be time out problem as you sais it is finite but as i trace and load connection from collectio at first it is connect but after seconds as i stay in Isend() it will disconnect and my stream writer can not write to dispose object so if the problem is from timeout how should i do that. so any buddy has any idea, thanx 4 ur help; and here is the code. } here is my server class and send function class Server : packetizer { #region Variable Scope private Socket socket; private TcpListener tcpListener ; private Thread listenThread ; private Queue thread_Queue ;//it keep thread id inorder to dispose after disconnection private delegate void setText (string str); private TextBox Logger; private static int ConnectID; private Connection_State CS; #endregion public Server(TextBox logger,Connection_State cs) //Constructor { Logger = logger; CS = cs; } public void start_Server () //Point to start Server { this.tcpListener = new TcpListener(IPAddress.Any, 1313); this.listenThread = new Thread(new ThreadStart(ListenForClients )); this.listenThread .Start(); }

private void ListenForClients () { this.tcpListener.Start(); Invoking_Logger("Server startlistenning..." ); thread_Queue = new Queue(); TcpClient client = null; while (true)

and here is COnnection stat class that hols my client information to reconnect to them i public struct { public public public }

CData Socket structSocket ; TcpClient structTcpClient; Thread structThread ;

class Connection_State {


#region Variable Scope private Hashtable Accepted_Client = new Hashtable(); public CData ClientHolder = new CData(); #endregion public Connection_State () { } public Hashtable Acp_Client { get { return Accepted_Client ; } set { Accepted_Client = value; } } //Add new client that connect to sever to this HashTable public void Add_To_Acp_Client(int ConnectID , CData structtcpthread) { Accepted_Client.Add(ConnectID, structtcpthread); } }

i Reply Perry posted 4 years ago Don't know if I'm asking the same as the guy above me, but I'm asking it more simple anyway. How do I send to all connected clients? I've tried adding all tcpClients to a list and I tried to send to their streams, but unfortunatly I don't recieve a thing in my client, while I can send data back to a single client upon connection... Here's the 'sending' code: public void sendToClient (String line, TcpClient client) { try { NetworkStream stream = client.GetStream(); ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder.GetBytes (line + "\0");

stream.Write(buffer, 0, buffer.Length); stream.Flush();

} catch { connClients.Remove(client); myInterface.logTxt.Invoke(new AppendTextDelegate (writeIntoLog ), ("Client Disconnected ."+Environment.NewLine)); } }


public void broadcast (String line) { for (int i = 0; i < connClients .Count; i++) { sendToClient (line, connClients [i]); } myInterface .logTxt.AppendText ("Message broadcasted to " + connClients .Count.ToString( ) + " clients." + Environment.NewLine); } }

i Reply Benio posted 4 years ago Hi, I've made an application "client -> server communicator" made your way from the tutorial(btw.I LOVED IT!! All you need in an excellent compact form. Thank you for it!). I use it to send over a message to a PC in my company to start backuping itself. Everything works fine when I connect client and server to my router in the room, but when I take the PC for backuping downstairs where it belongs the server responds something similar to "Connection cannot be made as the server actively refuses it." The machines ping fine! I work in a large company with proxies and stuff and I assume the problem is the IT security, if so, how can I make the connection between the 2 PCs? - I really wouldn't want to involve IT "experts" responsible for security here to do it, as it would be done after 2012, and it'd be too late because it'd be after the end of the World :) ps. Thank you for the tutorial. If the application works maybe I'll get a raise :) Cheers, Benio

i Reply Feez posted 3 years ago I am in trouble. Is it possible that same client and same server creates mutiple connection. Because i need to know the status of same client multiple request response from server. so that there won't be any business loss.

i Reply cdutoit posted 3 years ago Hi, I am trying to send an acknowledgement back to the client once they have sent a message to the server. I where should I add the code below to the HandleClientComm to get it working? byte[] buffer = encoder .GetBytes("Hello Client! Message Received!" ); clientStream.Write(buffer, 0, buffer.Length); clientStream.Flush();

HandleClientComm private void HandleClientComm (object client) { TcpClient tcpClient = (TcpClient)client;


NetworkStream clientStream = tcpClient .GetStream(); byte[] message = new byte[4096]; int bytesRead ; while (true) { bytesRead = 0; try { //blocks until a client sends a message bytesRead = clientStream .Read(message, 0, 4096); } catch { //a socket error has occured break; }

if (bytesRead == 0) { //the client has disconnected from the server break; } //message has successfully been received ASCIIEncoding encoder = new ASCIIEncoding (); System.Diagnostics.Debug.WriteLine (encoder.GetString(message , 0, bytesRead)); }

The listener on the client does not pick anything up if I just add it below the System.Diagnostics.Debug.WriteLine(encoder .GetString(message, 0, bytesRead ));

Not sure what I am missing?

i Reply MRB posted 3 years ago thank you for tutorial but in this part client.Connect(serverEndPoint );

it has error no connection could be made because remote machine refused it can someone help me ? MRB 3 years ago sorry, I had stupid mistake :) anonhj one year ago hello, i face the same problem as well, how you solve it? can tell me??


thanks.. fwsteal posted 3 years ago i read the article and seems good; have a question about getting the data back from the server. How do i do that? I have two code files below: client form -- windows form with a textbx for remote ip address and port; button for connect to device; status txtbox based on connection; message txtbx to send to remote sever; send button; message received txtbox. client.cs using using using using using using using using using using using using using using

System; System.Collections.Generic; System.ComponentModel ; System.Data; System.Drawing; System.Linq; System.Text; System.Windows.Forms; System.Collections ; System.Threading ; System.Net; System.Net.Sockets; System.IO; System.Net.NetworkInformation ;

namespace TCPServerTutorial { public partial class Client : Form { IPAddress ip; const int port = 1234; string myIP = string.Empty; string strMode = string.Empty; string strAddress = string.Empty; TcpClient client = new TcpClient(); Server server = new Server(); public Client() { InitializeComponent(); txtbxIPAddress .Text = "192.168.10.147" ; txtbxPort .Text = "1234";

server.cs using using using using using using

System; System.Collections.Generic; System.Linq; System.Text; System.Windows.Forms; System.Net.Sockets;


using System.Threading; using System.Net; namespace TCPServerTutorial { class Server { //a simple threaded server that accepts connections and read data from clients. private TcpListener tcpListener ; //wrapping up the underlying socket communication private Thread listenThread ; //listening for client connections const int iPort = 3000; //server port public Server() { this.tcpListener = new TcpListener(IPAddress.Any, iPort); this.listenThread = new Thread(new ThreadStart(ListenForClients )); this.listenThread .Start(); } private void ListenForClients () { this.tcpListener.Start(); //start tcplistener //sit in a loop accepting connections while (true) { //block until a client has connected to the server

Any help would be great. Thank you.

i Reply An on 999 posted 3 years ago Hi. Thank you for an excellent example! However, I am having a problem, I want my server to send a short string to each client as they connect to the server, but I keep getting this error on "NetworkStream.Write": Specified argument was out of the range of valid values . Parameter name: size

Here is my code: class Network { private const int bufferSize = 8192; private private private private

IPEndPoint serverEndPoint ; TcpClient tcpClient = new TcpClient (); NetworkStream netStream ; Thread receiveThread;


public delegate void MessageReceivedHandler (string message ); public event MessageReceivedHandler MessageReceived; public Network (string ServerAddress, int ServerPort ) { try { serverEndPoint = new IPEndPoint (IPAddress.Parse(ServerAddress), ServerPort ); } catch (Exception e) { MessageBox.Show(e.Message); } }

public bool ConnectToServer() { try { tcpClient .Connect(serverEndPoint ); } catch (Exception e) { MessageBox .Show(e.Message);

I have been googling, but not been able to find anything that would explain why I keep getting that error. Thankful for any help you can give me! An on 999 3 years ago Ahhh, too early in the morning here for me ;) Here is my server code: class Network { private const int bufferSize = 8192; private TcpListener tcpListener ; private Thread listenThread ; List clientThreads = new List(); List clientList = new List(); public delegate void ConnectionEstablishedHandler (TcpClient tcpClient ); public event ConnectionEstablishedHandler ConnectionEstablished ;

public void StartListening() { tcpListener = new TcpListener(IPAddress.Any, 3333); listenThread = new Thread(new ThreadStart (ListenForClients )); listenThread .Start(); } public void StopListening (bool DisconnectAll )


{

tcpListener.Stop(); if (DisconnectAll) { foreach (TcpClient tmpClient in clientList) { tmpClient .Close(); } }

}

Brandon Cannaday 3 years ago I noticed a potential problem in your code. You allocate buffer to the size of 8192, then immediate set the reference equal to the output of encoder.GetBytes. Next, while reading from the client, your attempting to read 8192 bytes into a buffer that's now much smaller. tleylan posted 3 years ago Just a quick note to offer a solution to the blocking call to AcceptTcpClient(). The TCPListener class has a Pending() method indicating whether there is a client to accept. I added a Boolean property "listening" to control the loop (rather than using "true"). Inside the loop there is a call to Pending() and only if that returns true is there a call to AcceptTcpClient() which should not block. When you need to stop the server set Listening to false. The loop exits and we an opportunity to call tcpListener.Stop(). Log files confirms that it is working for me...

i Reply An on ymou s posted 3 years ago I just want to share what I'm doing. I made a chat program/application(with GUI) using C#.NET and I used your codes as reference, it's working fine. I don't actually have an error or problem with my codes. I used the server as bridge only and I can broadcast messages sent from one client to all clients connected. Then I modified it, added some feature and made it work like yahoo messenger or skype but for a local area network only. I have login, registration and I am now working for private messages and adding friends(accepting or rejecting requests). Clients can only use the application if the server is executed on my computer because the ip I set for the clients is my ip. Now, I have some questions. Is it possible to broadcast the server's IP so that I won't use a default/fixed ip address for the clients to connect? If yes, how will the clients get/search the server's ip? If I want to make another chat application and I want to make it that it won't matter who logs in first, will it be possible to make every client the server themselves? How will they connect to each other? I already had done this using VB6 but with the use of winsock.

i Reply Massi636 posted 3 years ago Stop problems; this is may way after have read all posts: added [language] server.Stop()[/language] that simply do a [language]this.tcpListener.Stop();[/language] from the closing event of the main form. Then added [language] List clientList = new List();[/language] and added a client in my collection each time a


[language]clientThread.start();[/language] then catch the exception in the[language] while(true)[/language] and close all client in the list. I suggest to check with processExploer: it's working fine! Many thanks!

i Reply Hans posted 3 years ago This is a good article and still valid today. But you should use the ThreadPool instead of creating a new Thread every time when listening. This will reduce a lot of stress when receiving messages and it will prevent the CLR from having to perform many garbage collections due to a lot of discarded threads. Brandon Cannaday 3 years ago In most cases you are correct. The ThreadPool does have a limited number of threads (this can be changed). If the app is handling hundreds or thousands of clients, the ThreadPool will queue your request indefinitely until a thread becomes available - which may never happen if clients aren't disconnecting. ak.naser posted 3 years ago Your program is well work in local net work. but failed in internet.

i Reply ak.naser posted 3 years ago i want a clear article for TCP server / Client run over inter net any one help me

i Reply An on ymou s posted 3 years ago The Reddest, How can I send some data back to a client and then read that data? I can't seem to get the code you supplied to work. Could you provide some working example code for me to study please? Thanks.

i Reply Francisco posted 3 years ago Excellent tutorial. Do you have something similar for a threaded client?

i Reply Maurici o Sierra posted 3 years ago Gracias men! me sirvió mucho! excelente ejemplo para empezar a programar! Como puedo hacer mas segura la conexión TCP para evitar hackers? Thanks man! served me! excellent example to start programming! How I can make more secure TCP connection to prevent hackers?

i Reply


anvas posted 3 years ago Hi, u guys amazing Advance Thanks

i Reply An on ymou s posted 3 years ago Nice! And easy to package with a NotificationAreaIcon application so that everything is not just available at your fingertips, but its activity is visible just by changing the icon! A nice little addition would be including a named pipes server both client-side and server-sode, so that you can not just run information around from machine to machine, but target other objects on any specifc machine that listen to the pipe server.

i Reply Jo e posted 3 years ago The first comment was over 3 years ago and they've been ticking away ever since. It's not just that the code is clear, it's that the explanations were written clearly too. Excellent work! I loathe the trite "help me write tcp server program! give me code!" comments. Many questions can be answered by reading through the comments before you post. Although, after 3 years that's getting a bit time consuming. :)

i Reply An on ymou s posted 3 years ago Any working examples of client reading/receiving data from server..?? I think I have the right code for the server to send data, but not sure how or what event the client uses to receive. Thanks

i Reply rkrijger posted 3 years ago Thank you for this great example! I found it to be very useful. A few questions will arise, though: Why not use: private void HandleClientComm (TcpClient client)

Instead of private void HandleClientComm (object client)

?!?

i Reply rkrijger posted 3 years ago Never mind... It doesn't compile with "TcpClient" instead of "object". Sorry.

i Reply


An on ymou s posted 3 years ago how I can create a tcp server in c # .Net using MFC serialization of messages

i Reply An on ymou sFF posted 3 years ago how I can create a tcp server. Net c # receive and reply to messages MFC serialization

i Reply Ag ehac k posted 3 years ago i'm using oscar protocol as used in icq. it's so easy to send ANy data any length with FLAP format. good article. =)

i Reply boyparka posted 3 years ago Hi there, Just a quick thanks for an excellent tutorial. It helped me out a lot.

i Reply santhosh posted 3 years ago hey first of all excellent tutorial. I am trying to create a GUI socket server. The goal is simple. 1.Open a port 2.keep sending data to the port 3.the data is given from a textbox in the gui and must be sent after the button is pressed. 4.Do NOT CLOSE THE CONNECTION to the port until a button is pressed in the GUI. I have done some part of it but the problem i m facing with my code is i am not able to split the accept client connection part from the send data to client part. Hence each time i click my button to send the data i have to close the connection and open a new connection again. Please help me with this. The code below executes on button press. As you can see each time i have to close the socket and redo everything on each button press. I am not able to split it into parts. Please help me. Socket socket = new Socket(AddressFamily.InterNetwork , SocketType.Stream, ProtocolType .Tcp); IPEndPoint ip = new IPEndPoint(IPAddress.Any, 9999);

socket.Bind(ip); socket.Listen(10); Console.WriteLine ("Waiting for a client...");

Socket client = socket.Accept(); IPEndPoint clientep = (IPEndPoint)client.RemoteEndPoint; cliStatusLbl .Text = "Connected with Client" ;


string sndCmd = "|" + this.keyTxt + "|" + this.valTxt + "\n"; byte[] data = new byte[1024]; data = Encoding .ASCII.GetBytes(sndCmd);

client.Send(data, data.Length, SocketFlags.None); Thread.Sleep(2000);

client.Close(); socket.Close();

i Reply David S posted 3 years ago I solved the same thing using the asynchronous calls built into the object. This will leverage the thread handling built into .Net and you should have less issues with hanging threads. I tested this as part of a HTTP handling program and it was lightening fast and definitely was using multiple connections at the same time. using System; using System.Net; using System.Net.Sockets; ///
/// Multithreaded routine to handle concurrent Tcp connections on a single endpoint ///
public class TcpHandler { public bool listening ; public TcpListener listener; public void Main() { Byte[] ip = {127, 0, 0, 1}; IPEndPoint endPt = new IPEndPoint(new IPAddress(ip), 3000); this.listener = new TcpListener(endPt); this.listener .Start(); Console.WriteLine ("Listening");

this.listening = true; listener.BeginAcceptTcpClient (HandleRequestAsync , null);

Console.WriteLine ("Press 'Enter' to exit..." ); Console.Read(); listening = false;

listener.Stop(); } public void HandleRequestAsync (IAsyncResult ar)


i Reply Gulshan Garg posted 3 years ago Hey Dear, Please send me a server side code to communicate with client, get data from client end and send data to client end while a number of clients are online. With Thanks

i Reply mahdi87_gh posted 3 years ago Hi all my friends thanks for this good article. i want to send a dataTable object through tcp/ip from client To server. by this article ,now i can send text from client to server, but i don't know how to send dataTable? if i convert dataTable to byte[] and it's size become more than buffer size, my data will split into two or more packets. how should i merge them on the server? please help. thanks

i Reply Chris posted 3 years ago ///
/// Great tutorial ///
/// Extra time for a cold beer. public bigInt Thanks();

i Reply Barter posted 3 years ago Hi, The tutorial was great and very helpful, but I'm making a server system for some kind of group chat thing, but I have no idea how I can have the client-side application listen for messages getting recieved from the server.

i Reply An on ymou s posted 3 years ago Hi, OK I'm sure this tutorial is great but I can't get it to work. I've been searching online for 90 minutes and I can't find a simple WORKING program that I can simply cut and paste into Visual C#2010 and get to work. Can you please make a simple program that on button1 click runs the server code, button 2 click runs the client code, and button3 sends text from client to server. That way one simple program does it all. I'm going nuts that I cant find a working example that does that. (well i found one that is a console application). Thanks. An on ymou s 3 years ago button 1: server private void btnServerCreate_Click(object sender, EventArgs e) { if (TCP_Server == null) { TCP_Server = new Server();


// Ereignishandler aufrufen wenn eine Message empfangen wird TCP_Server.MessageReceived += new Server.MessageReceivedHandler(Message_Received); btnServerCreate.Enabled = false; } } button 2: client private void btnClientSend_Click(object sender, EventArgs e) { TcpClient client = new TcpClient(); //IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 3000); IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("192.168.2.105"), 3000); client.Connect(serverEndPoint); NetworkStream clientStream = client.GetStream(); ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder.GetBytes("Hello Server!\r\n"); clientStream.Write(buffer, 0, buffer.Length); clientStream.Flush(); } An on ymou s posted 3 years ago Hello, This approach creates one thread per client. I am curious if this is the way to go. I'm been trying to find articles on recommendations to the max number of tasks. If I had 100 users logged on at once, hence 100 threads, is this ok or will I hit performance issues. Brandon Cannaday 3 years ago The number of threads is unlikely to be a performance concern. It depends on what your server is doing, but a basic chat server could probably handle thousands of clients. Aar on posted 3 years ago I'm having a peculiar problem where clients can connect, but are sometimes automatically disconnected. This happens on/off with periods ranging from minutes to hours in which clients are automatically disconnected right after they connect. I've left the original code exactly the same, and have only added some Console.WriteLine calls to elaborate. This is what the console reads: --- Client connected at 5- 5-2011 Client disconnected --The connection also does NOT show up in netstat after this happens. I'm using a flash application running from a webserver on the same device to connect to the server. The flash code to connect looks like this: xmlsock = new Socket(); xmlsock.addEventListener (ProgressEvent.SOCKET_DATA, serverData); xmlsock.addEventListener (Event.CLOSE, connectionLost ); xmlsock.addEventListener (IOErrorEvent .IO_ERROR , ioError ); xmlsock.addEventListener (SecurityErrorEvent .SECURITY_ERROR, securityError ); xmlsock .connect ("SERVER_IP", 3000); //omitted the actual ip, for obvious reasons

What's mostly eating me about this, is that it appears to be completely random. I've found no consistent failure/success, not with browser types, specific computers, IP's, OS's, etc. They all fail/succeed periodically. Aar on 3 years ago Failed to note one thing: there is also no socket error on the server-side. It simply breaks out of the


while loop due to bytesRead being 0. It makes me wonder if there is anything about the actionscript side of this that might be causing such instability, like the Read call returning early and having read nothing. Aar on 3 years ago Also confirmed through a remote desktop connection to the server, that the problem only happens when trying to connect from outside of the server's network. Upon logging onto the server, I opened a web browser, went to the website address that is pointing to the webserver's IP, and attempted a login. This worked fine. Tried the same thing from my own PC, got disconnected right away. What could be causing these disconnects, if not the software itself? All my firewalls are open, and I have a public IP address on the server (which connects directly to the ISP, ergo there is no router) Aar on 3 years ago I found a workaround for my problem. It turns out there was something about the circumstances of the initial connection attempt that caused the connection to destabilize. I implemented a once-a-second ping message from the client, and if it didn't receive a pong within a few seconds it would disconnect and try to reconnect to the server. Subsequent connections are stable for some reasons. I'm still unclear as to why the initial connection is predominantly severed, but it could have something to do with the fact that it's done almost immediately after the SWF starts running. stes posted 3 years ago Thanks a lot for this tutorial! In order to get started with the issue, I searched for a quick and plain tutorial. Well, let's say I was not disappointed!

i Reply Hari posted 3 years ago Hi, How do i test this with client sending data and server returning back? I am using Visual studio 2010 and i created a console application for server. Then , i created another console application for the client inside the same solution . And when i run the solution, nothing happens. Am i missing something ?

i Reply eyal82 posted 3 years ago Hey Brandon, I have a problem figuring out how to send a message from client to client through the server with threads. For example suppose i have two clients(A and B) connected to the server, and i want to send a message from client A to client B. So at this moment in the server i have two threads(T1 and T2) for the two clients and the two threads are blocking at read(). Now im doing this: 1. Client A sending a message to the server (with data and client B id). 2. The server recieve the message in thread T1(client A thread). 3. The server gets client B id from the message. 4. The server finds client B from the clients collection, and gets his NetworkStream. 5. The server sends the message using this Stream with write(). 6. The server goes back to read() in this thread(T1).


The questions are: 1. Is it ok that all of this was made in thread T1? I mean is it ok that im also communicate with client B through thread T1? or should i somehow tell thread T2(client B thread) to send the message to client B? 2. Is it a problem that client B networkStream is used in thread T2(blocking with read()) and also in thread T1(with write())? I really would appreciate if you could help, thanks! Eyal Brandon Cannaday 3 years ago The threads in the server should primarily be used to read from the clients. They should rarely be interrupted for other tasks. ?1. Since communicating with client B could take up to 30 seconds (or whatever your timeout is), I would not recommend using T1 to send the information. You'd be blocking yourself from reading any communications from client A while you're attempting to transmit to B. I would recommend having another 'transmit' thread for each client and a queue where messages to transmit could be added. T1 would receive a message, get client B's queue, add the message, and the return to reading. client B's transmit thread would continually be pulling messages out of the queue and sending them. ?2. The NetworkStream object can be read and written simultaneously from different threads. I don't think multiple threads can safely write to it simultaneously, so whenever you're using it for writing, just surround it with a lock. eyal82 posted 3 years ago thank you for the fast reply, ok so for each client i will have a "read" thread and a "transmit" thread. ?1. Do you recommend to maybe add another thread for each client that would acutualy do the work? i mean after the "read" thread gets the message it adds it to a "jobs" queue, the "doWork" thread would continually be pulling messages out of this queue, do the actual work according to the protocol and prepare a resultMessage, then adds the resultMessage to the destination client "messageToTrensmite" queue that the "transmit" thread will send to the client? ?2. When you say "the transmit thread would continually be pulling messages out of the queue" you mean that it continually keep chacking if the queue is not empty? something like: while(true) { if(!queue.isEmpty) { //handel message } }

or maybe its better if some event will trigger it to check the queue? Brandon Cannaday 3 years ago ?1. I don't think another thread would be necessary for handling the message - unless the contents of doWork could take a while and begin blocking the read thread. If all you're doing is parsing the protocol and building a simple response, I think the read thread can do that. ?2. Polling the queue would be fine and probably the simplest approach (I'd stick a sleep in there somewhere though). Here's an article talking about a blocking queue, which would essentially block the thread until something was enqueued - this is probably the most correct solution, but is more difficult to implement. Pool Eng posted one year ago Hello Reddest: I come From ROC(Taiwan). This is a good example better than MSDN. It's quite simple and


clean,thanks for this Tutorial

i Reply shafyxl posted one year ago Beginners!! better to see the MSDN example fist http://msdn.microsoft.com/enus/library/system.net.sockets.tcplistener(v=VS.90).aspx.

i Reply Louhike posted one year ago Great example ! The code is well written and simple and we easily understand everything just by looking at the code. Thanks a lot, it's really helpful.

i Reply Mouayad AL ZEIN posted one year ago First of all, thanks a lot for your article, it helped me a lot in understanding the whole concept. I have one question : Let's suppose I want to build a Server class and a Client class using what you have written in your article, I still can't figure out how to make a Client class so that each time I create a client object I can connect it to the Server ? Your code shows pretty well how to define a server that listens to clients, but how do I launch the clients ? my question might seem stupid to you, but I'm new to networking and I need an answer badly. Best Regards Brandon Cannaday one year ago Here's the shell of a possible client class that may help you out a little. public class Client : IDisposable { TcpClient _tcpClient;

// Connects the client to a server at the specified // IP address and port. public void Connect(IPAddress address , int port) { _tcpClient = new TcpClient(); IPEndPoint serverEndPoint = new IPEndPoint (address, port);

_tcpClient.Connect(serverEndPoint ); // Create a thread to read data sent from the server. ThreadPool.QueueUserWorkItem ( delegate {


Read(); }); }

// Sends bytes to the server. public void Send(byte[] buffer) { _tcpClient.GetStream().Write( buffer, 0, buffer.Length);

_tcpClient.GetStream().Flush(); } private void Read()

rakesh posted one year ago thank u so much for this post.. this really helped me a loooot......

i Reply remlap21 posted one year ago Excellent article thank you so much!

i Reply An on ymou s posted one year ago HI first sry my english. This is a good example but my client has had several requests.when the server responded with GetBytes() how I jump to the next client request?getstring() An on ymou s one year ago i mean this: -client send to server -server answer and wait for next request and answer etc. An on ymou s posted one year ago I used your code and my Console just sits there and does nothing... An on ymou s one year ago Never mind Yehonatan posted one year ago Hi,im starting to learn c# again and i wanted to ask something. On the article above you gave us the directions to create TCP server but what if i want to create TCP client? where can i learn how to create one and not just to copy and paste code? Thanks. BTW - your captcha is easy to break if someone using php.

i Reply An on ymou s posted one year ago


Iam getting following error at this.tcpListener.Start(); system.collections.listdictionaryinternal An attempt was made to access a socket in a way forbidden by its access permissions.. Please can any one help..

i Reply An on ym ymou ou s poste posted d one year ago hi, im starting to learn on c# client server socket programming. sorry a dumb question.. is your code a multithreaded server socket programming? a server connect by many clients? thank you.

i Reply An on ym ymou ou s poste posted d one year ago Sorry for being a newb but how do I treat every client if I want to send something to them?

i Reply antonio poste posted d one year ago Hello First of all thank thanks s for the tutorial tutorial it was really really helpful to understand tcp. I'm working in a monitoring application based in a Modbus TCP IP communication model, the client has a timmer that sends one command to read the registers in the remote server, and the server recives the command and sends back the information, the fact is that I dont know if I should use synchronous or asynchronous calls. thanks

i Reply posted poste d one year ago Nice explanation, thanks....!!

i Reply ch0eb1t poste posted d one year ago allright, I found a very bad problem. when I close the program by clicking the x button on the top right corner of the winform, after starting the thread of course. The listener is still running and you can see it with the task manager. manag er. if you use the build mode, the IDE won't exit from the build mode except when you stop it. or if you're using (ctrl+F5), do it again, and it will give you an error. This problem's so bad. even though the thread and program is closed, the this.tcpListener.AcceptTcpClient(); line is still running. Brandon Ca Cannaday nnaday one year ago Yep, the code here is not feature feature complete, just just a shell. When the app close closes, s, just call Stop on the TcpListener.


ch0eb1t one year ago I'm sorry, but can you please tell me where to put the tcplistener.stop whenever I close the program? :) the server code is written in different class from the main winform app. The server thread is created when I clicked a "Start" button. I'm trying to solve this problem but I'm getting a dead end. Brandon Ca Cannaday nnaday one year ago The server class should should expose some way to start and stop it. public class Server { public void Start Start() () { // Called by the application when the // start button is pressed. } public void Stop Stop() () { // Called by the application when it // it closed. } }

view all 4 comments comments

anonhj poste posted d one year ago thanks thank s for the code i have error in this: client.Connect(serverEndPoint); i dont know how to solve solve it, can help me on it. thanks again. ch0eb1t one year ago does the client code run on different machine? anonhj one year ago yes, i try to run it on different machine and also run on same machine. For now, the error was solved, but, both client and server seem not connect to each other, i post my code down there, if possible please check for me. thanks a lot. ch0eb1t one year ago change the 127.0.0.1 on the client program to your server PC IP address posted d one year ago BlueButtons poste Hello, i was wondering, how do you connect to computers that have a different IP address. For instance, if i want to run your client and server seperately on two different machines, loopback (or using the localhost) won't allow for this.... Not too familiar with networking, any help would be greatly appreciated!


ch0eb1t one year ago The two computers computers must be on the same LAN consider it: Computer A IP address : 192.168.0.5 running the server code Computer B IP address : 192.168.0.6 running the client code in Computer B, change: IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 3000); with IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("192.168.0.6"), 3000); anonhj poste posted d one year ago hi, i had been tryin trying g out the code, no error, but dont know why both client and server are are not connec connectt to each other, nothing response, something wrong in my code, please help me, thanks a lot. server code using using using using using using using using using using using using

System ; System; System. System . Collections Collections. .Generic Generic; ; System. System . ComponentModel ; System. System . Data Data; ; System. System . Drawing Drawing; ; System. System . Linq Linq; ; System. System . Text Text; ; System. System . Windows Windows. .Forms Forms; ; System. System . Net Net; ; //networking System. System . Net Net. . Sockets Sockets; ; //networking System. System . Threading ; //networking System. System .Net Net. . NetworkInformation ; //monitor bandwidth

namespace NBCS_serverlogin { public partial class NBCSadmin : Form { private TcpListener TcpListener tcpListener tcpListener ; private Thread Thread threadTcp threadTcp ; static NetworkStream clientStream ; const int int portnumber portnumber = 3333 3333; ; //public delegate void ChangedEven ChangedEventHandler(obj tHandler(object ect sender, EventArgs e); // public event ChangedEventHandler ChangedEventHandler Changed;

public NBCSadmin () { InitializeComponent (); portnotxt . Text = "3333" "3333"; ; // initiateLi initiateListen(); sten(); }

client code


using using using using using using using using using using using using

System; System.Collections.Generic; System.ComponentModel ; System.Data; System.Drawing; System.Linq; System.Text; System.Windows.Forms; System.Net; System.Net.Sockets; System.Threading ; System.IO;

namespace NBCS_Client { public partial class NBCSuser : Form { static TcpClient clientuser; IPEndPoint serverEndPoint ; NetworkStream clientStream ; const int portnumber = 3333; string myIPAdd = string.Empty; string strgAddress = string.Empty; public NBCSuser () { //InitializeComponent(); InitializeComponent (); ipaddtxt.Text = "127.0.0.1"; portnotxt .Text = "3333";

}

i Reply um m posted one year ago After i have used the send method from server, how do i open that message on client?

i Reply Mikki posted one year ago What do you mean by the word "block?" That it stops waiting for clients until one has connected? Brandon Cannaday one year ago In this case, block means execution will not continue until a client connects or an error occurs. BAJA posted one year ago someone can put a link whit a functioning code, because i am nuub and y dont undertant so well

i Reply


eyal82 posted one year ago Hey Brandon, I know this is a bit out of scope but can you show how to add SSL support if its not too complicated?

i Reply hossam posted one year ago NetworkStream clientStream = tcpClient .GetStream(); ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder .GetBytes("Hello Client!" ); clientStream.Write(buffer, 0 , buffer.Length); clientStream .Flush();

I got an error in the last two lines

i Reply antonio posted one year ago Hello I'm new in C++ and I'm working on the client code but I always get the same error C3364: 'System::Threading::ParameterizedThreadStart' : invalid argument for delegate constructor; delegate target needs to be a pointer to a member function I also tried with ThreadPool::QueueUserWorkItem(delegate Read_Multipl_Reg(direccion, unidad, referencia,cantidad,registros)); but it doesn't work either can someone help me to see how to solve it thanks #pragma once #include "stdafx.h" #include #include #include #include #include #include #include using std::cout; using std::cin; using namespace System; using namespace System::Text; using namespace System::Net; using namespace System::Net::Sockets; using namespace System::Threading;

public ref class cliente


{ TcpClient^ ClienteMBTCP ; Thread^ hilocliente ; int cantidad; int unidad; int referencia; String^ direccion ; array^ registros; public: cliente(){ } public: void Connect(String^ address , int port)

i Reply scriptinphp posted one year ago Great Tutorial. question though, kinda of off topic, but here goes: I am in need of a traceroute application, and have found source for one, but I have tried changing it to use TCP (with my extremely limited knowledge). Is there any way you could help with conversion to work with TCP vs UDP? http://dice.neko-san.net/2011/01/my-traceroute-for-windows/ you can respond to me at \^\^ gmail.com

i Reply An on ymou s posted one year ago hi, first of all, nice tutorial! im new to client/server programming. but i was wondering if you could help me with a project im working on. i'm trying to send a video file from client to server which is 20 megs big. my question is, what do i need to change in the code to be able to stream video? and how do i split the bytes instead of sending it all at once? thanks in advance!

i Reply An on ymou s posted one year ago hi,i have to write a multithreaded connection oriented server using C/C++ and gcc.the server should be able to handle multiple clients concurrently and simulate it for a minimum of ten concurrent clients

i Reply An on ymou s posted one year ago


Awesome walk -through. This is the simplest explanation of C# Tcp that I have read. Very nicely done!

i Reply maryam posted one year ago thank you. best regard for all friend

i Reply An on ymou s posted one year ago hi every one, i have designed an instant news sending application for our customers.(using c# socket and async methods.) The server accepts the connection and keeps them in a list as connected users. When a news is entered to database, the server program sends the news to the connected users. In here, the client should stay connected whole day to recieve the news when added. I want to ask is there any time limitation for the connection to be alive. If 3 hours no news entered, then are the connections still alive and ready to recieve ? I am not asking to reconnect when disconnect conditions occurs. I have implemented those exceptional scenarios to reconnect. I searched too much but i could not find the answer i am looking for.

i Reply Mike Hometchko posted one year ago For those of you who are looking for a simple two-way communication resolution (and I've seen a ton of posts requesting it) I'll post my code here. Server public class Server { private TcpListener tcpListener ; private Thread listenThread ; public Server() { this.tcpListener = new TcpListener(IPAddress.Any, 3000); this.listenThread = new Thread(new ThreadStart (ListenForClients )); this.listenThread .Start(); } private void ListenForClients () { this.tcpListener.Start(); while (true) { //blocks until a client has connected to the server TcpClient client = this.tcpListener.AcceptTcpClient(); //create a thread to handle communication //with connected client Thread clientThread = new Thread(new ParameterizedThreadStart (HandleClientComm ));


Thread clientThreadSend = new Thread(new ParameterizedThreadStart (HandleClientComm ) );

clientThread .Start(client); clientThreadSend .Start(client); } } private void HandleClientComm (object client) { TcpClient tcpClient = (TcpClient)client;

Client public class Client { TcpClient _tcpClient;

// Connects the client to a server at the specified // IP address and port. public void Connect(IPAddress address , int port) { _tcpClient = new TcpClient (); IPEndPoint serverEndPoint = new IPEndPoint (address, port);

_tcpClient.Connect(serverEndPoint); // Create a thread to read data sent from the server. ThreadPool.QueueUserWorkItem ( delegate { Read(); }); }

// Sends bytes to the server. public void Send(byte[] buffer) { _tcpClient.GetStream().Write( buffer, 0, buffer.Length);

_tcpClient.GetStream().Flush(); } private void Read()

Hope this helps! An to n 10 months ago Thank you very much, it really helped. jac k 6 months ago Can you give me example of the code, my code is not working well...


nikos posted one year ago hello, im new in Promela and i have to simulate the TCP/IP connection management with flow control in Promela and i need help. thnx.

i Reply Piyush Dixit posted one year ago Hi, Thx for the code it is working great. my problem is when i try to invoke tcp server Application from my wcf service. i get the exception.. please help..

i Reply An on ymou s posted one year ago Quote of the day: 'although in practice this is limited because you can only spawn so many threads before Windows will get upset' Brilliantly put, Windows got upset with me recently as well.

i Reply MindHACKer posted one year ago This was very helpful, THANK YOU VERY MUCH.

i Reply An on ymou s posted one year ago Rectangle rect= new Rectangle(); rect.width = 10; rect.height = 10; rect.StrokeThickness = 1; rect.Stroke = Brushes.Black; Point startPoint= new Point(54, 52); Canvas.SetLeft(rect,startPoint .X); Canvas.SetTop(rect,startPoint.X); canvas.Children.Add(rect);

i Reply An on ymou s posted one year ago Dispatcher.Invoke(new Action(() => { canvas.Children .Add(rect); }));


i Reply Dilip Sharma posted one year ago Help Full Thanks For Post

i Reply An on ymou s posted one year ago My program gives an error with the TcpClient.GetStream() command. It doesn't recognize this function. Am I missing a declaration somewhere? An on ymou s one year ago Nevermind, found the problem - I had the t in tcpClient capitalized. GAWRRELL posted one year ago Hy, i have tested the tutorial and i get an error A first chance exception of t type 'System.Threading.WaitHandleCannotBeOpenedException' occurred in mscorlib.dll Additional information: No handle of the given name exists. Can anyone tell me how to fix this ? Brandon Cannaday one year ago What line of code throws the exception? An on ymou s posted one year ago I used u r code but, When I send some msgs from the client to server, i got an error " The calling thread cannot access this object because a different thread owns it." on this line " ASCIIEncoding encoder = new ASCIIEncoding(); txtContent.Textencoder.GetString(message, 0, bytesRead);" help me......... Am a beginner to the Socket pgming........

i Reply An on ymou s posted one year ago Thank you for the detailed and simple explanation. This is what I needed.

i Reply An on ymou s posted one year ago First..thank you for the post! I am working with the DataMax printer that is connected directly to the PC via network card. I have a TCP client tester that can send DPL commands to the printer and this part works well. However, I would like to add a Listner to get printer response. For example, when I send a command I should get back 3 blocks of eight bits each. My tester gets this reply but sometimes I need to send twice my command to get it. I think the listner that you are using would take care of it, but I am not sure how to use it in my app. My app is a simple windows form with one button, and response txt box.


Here is the link to the code I used in my app: http://msdn.microsoft.com/enus/library/system.net.sockets.tcpclient.aspx I made small changes to it as my app shows a form: void SendCommandToNetworkPrinter (String server, String message ) { try { // Create a TcpClient. // Note, for this client to work you need to have a TcpServer // connected to the same address as specified by the server, port // combination. Int32 port = System.Convert.ToInt32(txtPortId.Text); TcpClient client = new TcpClient(server, port); // Translate the passed message into ASCII and store it as a Byte array. Byte[] data = Encoding .ASCII.GetBytes(message);//System.Text.Encoding.ASCII.GetByte s(message); // Get a client stream for reading and writing. Stream stream = client.GetStream(); //NetworkStream stream = client.GetStream(); // Send the message to the connected TcpServer. stream.Write(data, 0, data.Length);

stream.Flush();

//Console.WriteLine("Sent: {0}", message); //MessageBox.Show("Sent:" + message); txtReply.Text += "SENT:" + message ; // Receive the TcpServer.response. // Buffer to store the response bytes.

i Reply An on ymou s posted one year ago Please note that NetworkStream.Flush() has no effect on the data in the stream. http://msdn.microsoft.com/en-us/library/system.net.sockets.networkstream.flush.aspx

i Reply LuisF posted one year ago Hi that´s a great explanation and a great code thank you very much. I have a question: How to get the IP address of the connected client?, I have looked to the tcpClient members but couldn't find any related option there and don´t know where could i get it


Thank a bunch! LuisF one year ago Ohh men, I´m not native English speaker, I have always thought that "Thanks a bunch" was thanks a lot, I just searched for for curiosity and found it was sarcastic sorry men, you know i meant thanks a lot! Danish Coder posted one year ago My new best friend ;-) Thx m8

i Reply Gio posted one year ago Very good essential example ! Thanks a lot !

i Reply An on ymou s posted one year ago Hello, Me I am having problem to handle an exception at the line NetworkStream clientStream = tcpClient.GetStream(); A NullPointerException.. I try to catch it by doing this: try{ NetworkStream clientStream = tcpClient.GetStream(); }catch { Console.WriteLine("An error /..."); } I can catch the exception but my program can not continue. it breaks at this level. How can I solve it??

i Reply Dias posted one year ago Very good post

i Reply rechim posted one year ago hey i have a question. i send a resuest from client to server, then the server send back to the client an answer. how to catch the servers respond into client? its the same thing like the server catch the message from clients? or what? thx Manish Ta 9 months ago have you got your answer, if yes please tell me. any other help are welcome this is really urgent thanks in advance mailid : [email protected] Gratefule posted 12 months ago Reddest: Just echoing what many others before me have stated, "EXECELLENT!". Too bad Redmond cannot find authors with your technical and explanation skills - I know, I searched many hours through MSDN


and came up empty. Gee, and I even pay for an MSDN subsription. Go figure!

i Reply An dy posted 12 months ago Hi Reddest, thank you for a great example. I do have one problem that I hope you (or someone else) can help me with. I've used your example to write a client and a server and it works great when both are running on the same pc, but when I try to run the client on another PC, then I cannot connect (this code line times out: client.Connect(serverEndPoint);) to the server. I'm on a corporate LAN and I've opened ports in the firewall on both PC's. Any help will be greatly appreciated! Here is some simplified code that I use to test the connection: //Client: using (TcpClient client = new TcpClient()) { IPEndPoint serverEndPoint = new IPEndPoint (IPAddress.Parse(ServerIp ), 14011); //client.Client. client.Connect(serverEndPoint ); using (NetworkStream clientStream = client.GetStream()) { Console.WriteLine("Connected? :" + client.Connected.ToString ()); ASCIIEncoding encoder = new ASCIIEncoding (); byte[] buffer = encoder .GetBytes("IDLE");

clientStream .Write(buffer, 0, buffer.Length);

clientStream .Flush();

clientStream .ReadTimeout = 29000; byte[] message = new byte[4096]; int bytesRead = 0;

bytesRead = clientStream .Read(message , 0, 4096); string msg = encoder .GetString(message, 0, bytesRead ); Console.WriteLine("Message: " + msg); return; }

} //Server: TcpListener tcpListener = new TcpListener(IPAddress.Any, 14011);

An dy 12 months ago Ok, I found a solution. The server runs as a service and I needed to setup the inbound rule in the firewall as described here: http://technet.microsoft.com/en-us/library/cc947797(v=ws.10)


The "normal" access to the firewall (Ctrl panel => win firewall) was not enough and the service's SID type was set to NONE instead of UNRESTRICTED. An on ymou s posted 11 months ago I am a noob and completely new to C#. I am more familiar with android but I need a server like this. Can someone post more exact instructions on creating this entire thing from the beginning. He did a good job of including the code but I have no idea as to where the code needs to be out in the project.

i Reply Sam Pearso n posted 11 months ago Hi, The Reddest, I've got a question about this. Suppose I've got this example running in its background thread behind a Windows Form. When I close the form, my program no longer exits, because the thread is waiting on tcpListener.AcceptTcpClient(). How can I solve this problem? I want my whole program to exit when I close the form. I tried calling listenThread.Abort(), but that doesn't work.

i Reply An on ymou s posted 10 months ago nice article

i Reply An on ymou s posted 10 months ago Im getting this error: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. At this line: bytesRead = clientStream.Read(message, 0, 4096); What am I doing wrong? The server and the client are my local machine. An on ymou s-No2 9 months ago I get the same error also, any solution on this? Manish Ta posted 9 months ago This is nice example I have a question i am able to send data from client to server, now server send back data to client how can i read this data sent by server to client. thanks in advance

i Reply Chuck Bland posted 4 months ago Has anyone implemented the change/suggestion from David S with the async handling? I think I understand what to do with it. It would help to see his solution completed. Specifically, does the thread handling in the original post remain the same, and would be placed where David S comments "//Handle the client connection here" ?


Chuck

i Reply Gal Ko s posted one month ago Hey, Brandon. I have achieved the sending message client -> server and actually connecting many clients simultaneously. But what I want to do is i.e. connect 2 clients and make them chat between themselves. And if 3rd client connects - then so he starts chatting with both other clients. The thing is that I don't know how to distinguish between the different clients' threads. This is my function: private void HandleClientComm (object client) { TcpClient tcpClient = (TcpClient )client; NetworkStream stm = clientList[n].GetStream(); msg = new TheMessage (); while (true) { Byte[] bSize = new Byte[sizeof(Int32)]; stm.Read(bSize, 0, bSize.Length); Byte[] bData = new Byte[BitConverter .ToInt32(bSize, 0)]; stm.Read(bData, 0, bData.Length);

msg = XmlRefactorServer .ByteArrayToObject(bData); String str = msg.Message; Console.WriteLine (str); stm.Flush(); // send back to client msg.Message = str; Byte[] bDataBack = XmlRefactorServer.ObjectToByteArray(msg);

stm = clientList[n].GetStream(); Byte[] bSizeBack = BitConverter .GetBytes (bDataBack .Length); stm.Write(bSizeBack, 0, bSizeBack .Length); stm.Write(bDataBack, 0, bDataBack .Length); stm.Flush(); }

where I have the array for storing clients objects TcpClient[] clientList = new TcpClient[100]; private int n = 0;

and after starting every thread I do this: TcpClient client = this.tcpListener .AcceptTcpClient(); if (n == 0)

C# Tutorial - Simple Threaded TCP Server - Tech.pro

Recommend Documents