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Building a C# Chat Client and Server

A step by step tutorial teaching you how to create your own chat client and chat server easily in C#, for local networks or the Internet.

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Geekpedia » C# Tutorials » C# Chat: Part 1 - Building the Chat Client

C# Chat: Part 1 - Building the Chat Client

In this two part tutorial you will learn how to create a chat client that connects to a chat server and exchanges messages with all the other connected clients. The first part covers the development of the client application.

On Saturday, October 20th 2007 at 12:43 PM

By Andrew Pociu (View Profile)

(Rated 4.5 with 137 votes)

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More C# Resources

» C# Chat: Part 1 - Building the Chat Client (currently reading)
» C# Chat: Part 2 - Building the Chat Server

Download the Chat Client Application project (Visual Studio 2005)

Building a Chat Server and a Chat Client

To no avail I've been searching the web for a good C# chat client/server application that is not thousands of lines of code long. The only simple ones I could find were flawed or very buggy, but then again I tried to combine the good parts of all the tutorials I found into one application, and one tutorial that you can see here today. We are going to build a fairly larger application (a few hundred lines of codes) than the ones we're used to here on Geekpedia, but we're still going to keep it simple. In fact, there will be two applications: one is a chat server, that handles incoming connections, stores them in hash tables, and distributes new messages to everyone connected, and the other is of course, the chat client, which connects to the server, sends messages and listens for incoming messages. A little knowledge of C#'s networking objects, multi-threading, events and delegates will definitely help you understand this tutorial more easily. A good way to start learning about delegates, events and creating client-server applications is to read the Delegates and Events in C# tutorial first.
The chat server will be able to accept as many chat clients as allowed by the hash table (and you are able to define the limit of the hash table yourself), and it will also track all the messages that are going back and forth in its own chat window, so you should be able to scale this code to a full blown chat application as long as you add the necessary error handling and the bells and whistles.

The client application

The client application is, as you might have expected, the simpler one, since all it has to do is to attempt to connect to the chat server, request an username, start listening for messages and sending its own, and finally disconnecting.
Start Visual Studio 2005 and create a new C# Windows Application. I've given mine the obvious "Chat Client" name.

Chat Client Form

The first two TextBoxes (txtIp and txtUser) will hold the IP address of the server we want to connect to and the desired username. Before testing out this code keep in mind to change this IP address to the one of the computer in your network that runs the client. If you read the Delegates and Events in C# tutorial, you probably assume you can run the chat application and the server application on the same machine, without needing two different computers connected through a network or the Internet. And you would be right.
The Connect (btnConnect) and Send (btnSend) buttons are obvious, they're for connecting to the server and sending messages. The large multi-line TextBox is named txtLog and it is where all the messages will be shown.The small TextBox at the bottom is called txtMessage and it is where the message to be sent to the server will be typed.

Now that we're done with the actual design of the form, we can finally code. Since we will be making use of networking, streaming and threading objects, start by adding the following using statements:

using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Threading;

We're going to declare most of our objects inside the class, as private, since we don't need them accessible from anywhere else outside the class:

// Will hold the user name
private string UserName = "Unknown";
private StreamWriter swSender;
private StreamReader srReceiver;
private TcpClient tcpServer;
// Needed to update the form with messages from another thread
private delegate void UpdateLogCallback(string strMessage);
// Needed to set the form to a "disconnected" state from another thread
private delegate void CloseConnectionCallback(string strReason);
private Thread thrMessaging;
private IPAddress ipAddr;
private bool Connected;

And now that we have them declared, let's put them to use. Let's start with the btnConnect_Click event which can be automatically generated if you double click on the Connect button. Inside it we're going to check whether or not we are connected to a server. If we are, we should call the method that initializes the connection, otherwise we call the method that closes the connection, also specifying a reason why to it:

private void btnConnect_Click(object sender, EventArgs e)
{
    // If we are not currently connected but awaiting to connect
    if (Connected == false)
    {
        // Initialize the connection
        InitializeConnection();
    }
    else // We are connected, thus disconnect
    {
        CloseConnection("Disconnected at user's request.");
    }
}

All simple so far, so let's move to InitializeConnection():

private void InitializeConnection()
{
    // Parse the IP address from the TextBox into an IPAddress object
    ipAddr = IPAddress.Parse(txtIp.Text);
    // Start a new TCP connections to the chat server
    tcpServer = new TcpClient();
    tcpServer.Connect(ipAddr, 1986);
 
    // Helps us track whether we're connected or not
    Connected = true;
    // Prepare the form
    UserName = txtUser.Text;
 
    // Disable and enable the appropriate fields
    txtIp.Enabled = false;
    txtUser.Enabled = false;
    txtMessage.Enabled = true;
    btnSend.Enabled = true;
    btnConnect.Text = "Disconnect";
 
    // Send the desired username to the server
    swSender = new StreamWriter(tcpServer.GetStream());
    swSender.WriteLine(txtUser.Text);
    swSender.Flush();
 
    // Start the thread for receiving messages and further communication
    thrMessaging = new Thread(new ThreadStart(ReceiveMessages));
    thrMessaging.Start();
}

Nothing too complicated happens in there. The IP address is parsed from the TextBox into an IPAddress object, and then we open a TCP connection to that address. The port is 1986 but it makes no difference as long as its free. We then prepare the controls on the form by disabling some and enabling the others. We also change the caption of btnConnect to now say Disconnect. Through a stream, we then tell the server which username we want, and immediately after that we start a new thread that calls the method ReceiveMessages() which will listen for incoming messages from now on. By putting this in a separate thread, our application is still fully usable while it is listening for messages from the server and keeping the connection alive.

It's time to see what the ReceiveMessages() method is all about:

private void ReceiveMessages()
{
    // Receive the response from the server
    srReceiver = new StreamReader(tcpServer.GetStream());
    // If the first character of the response is 1, connection was successful
    string ConResponse = srReceiver.ReadLine();
    // If the first character is a 1, connection was successful
    if (ConResponse[0] == '1')
    {
        // Update the form to tell it we are now connected
        this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { "Connected Successfully!" });
    }
    else // If the first character is not a 1 (probably a 0), the connection was unsuccessful
    {
        string Reason = "Not Connected: ";
        // Extract the reason out of the response message. The reason starts at the 3rd character
        Reason += ConResponse.Substring(2, ConResponse.Length - 2);
        // Update the form with the reason why we couldn't connect
        this.Invoke(new CloseConnectionCallback(this.CloseConnection), new object[] { Reason });
        // Exit the method
        return;
    }
    // While we are successfully connected, read incoming lines from the server
    while (Connected)
    {
        // Show the messages in the log TextBox
        this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { srReceiver.ReadLine() });
    }
}

A new stream reader is hooked up to the TCP client. It will listen for incoming messages. But first of all, we read the first line coming from the server. The reason for that is that we know the first line contains a response telling us whether or not we connected successfully. Two reasons why we might've not connected successfully are if we attempted to use an username that is already taken, or if we attempted to use Administrator as the username, which is reserved for obvious purposes. The first character of the response given by the server tells us through a 1 that the connection was successful, and through a 0 if it was unsuccessful. And in that case, it also reads a reason as to why it was unsuccessful. That reason starts at the 3rd character of the message, since the first one is the number, and the second one is a pipe character. For example: 0|Username is already in use. Now you can see why if the first character is not a 1 we read the string that starts at the 3rd character and ends at the end of the line.

The this.Invoke() calls tell the form to update itself. We can't directly update the form elements ourselves from this method because it's in a separate thread (remember we called it using ThreadStart()) and cross-thread operations are illegal.

Finally, the while (Connected) loop keeps calling the srReceiver.ReadLine() method which checks for incoming messages from the server.

Next comes the method that we kept calling using this.Invoke() - all it does is to update the txtLog TextBox with the latest message:

// This method is called from a different thread in order to update the log TextBox
private void UpdateLog(string strMessage)
{
    // Append text also scrolls the TextBox to the bottom each time
    txtLog.AppendText(strMessage + "\r\n");
}

So far we've seen how to receive messages from the server, but nothing about how to send them. When do we want to send a message? When the Send button is clicked or when the Enter key is pressed while txtMessage has the focus. This should be hooked up to the Click event of the btnSend button:

// We want to send the message when the Send button is clicked
private void btnSend_Click(object sender, EventArgs e)
{
    SendMessage();
}

And this needs to be hooked up to the KeyPress event of txtMessage:

// But we also want to send the message once Enter is pressed
private void txtMessage_KeyPress(object sender, KeyPressEventArgs e)
{

      // If the key is Enter 
    if (e.KeyChar == (char)13)
    {
        SendMessage();
    }
}

You can see that both of them make a call to SendMessage, which we are going to see next:

// Sends the message typed in to the server
private void SendMessage()
{
    if (txtMessage.Lines.Length >= 1)
    {
        swSender.WriteLine(txtMessage.Text);
        swSender.Flush();
        txtMessage.Lines = null;
    }
    txtMessage.Text = "";
}

Quite simple, isn't it? It just checks for the number of lines to be greater or equal to 1, and then writes that line to the TCP connection through the StreamWriter object. Calling Flush() ensures that the messages are being sent right away.

We seem to be almost done with the client application. But let's not forget that when btnConnect was clicked, if we were already connected, we called a method called CloseConnection() - what happened to that? Well here it is:

// Closes a current connection
private void CloseConnection(string Reason)
{
    // Show the reason why the connection is ending
    txtLog.AppendText(Reason + "\r\n");
    // Enable and disable the appropriate controls on the form
    txtIp.Enabled = true;
    txtUser.Enabled = true;
    txtMessage.Enabled = false;
    btnSend.Enabled = false;
    btnConnect.Text = "Connect";
 
    // Close the objects
    Connected = false;
    swSender.Close();
    srReceiver.Close();
    tcpServer.Close();
}

The form is being brought back to the not-connected state, and the TCP connection and streams are being closed. But what happens if the user doesn't click Disconnect and just closes the application while the connection with the server is alive? We surely don't want to leave the connection open like this till it dies by its own. Thankfully there is the ApplicationExit event that fires when the application closes, and that's where we can close our connection. To hook up the event change your Form1 constructor to the following:

public Form1()
{
    // On application exit, don't forget to disconnect first
    Application.ApplicationExit += new EventHandler(OnApplicationExit);
    InitializeComponent();
}

And here is the event handler that does the actual disconnection:

// The event handler for application exit
public void OnApplicationExit(object sender, EventArgs e)
{
    if (Connected == true)
    {
        // Closes the connections, streams, etc.
        Connected = false;
        swSender.Close();
        srReceiver.Close();
        tcpServer.Close();
    }
}

Believe or not, we're done with the chat client application. You should be able to compile and run it now, but of course there's nothing to connect to because we haven't developed the server. But that comes next in C# Chat: Part 2- Building the Chat Server. Here's a little teaser of our applications in action, with the server in the shadow of the two:

Chat Clients

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Current Comments

by Kahey on Wednesday, October 31st 2007 at 02:34 PM

Very good! Thank you for making it easy enough for an amateur coder to understand.
I\'ve been looking for a simple chat to incorporate into an online game (php/mysql, html/javascript) I\'ve spent months writing. I know there\'s no end of free ones to download however it\'s more satisfying to create ones own. Due to budget restrictions I\'ve coded everything thus far in good old notepad.
To this end I wonder is it possible to create a chat using javascript or php?

[Note: The cost of visual studio prohibits me from using C# at this point in my budget.]

by Andrei Pociu on Wednesday, October 31st 2007 at 05:49 PM

It is possible, the best approach would be to use PHP and JavaScript together to create a chat using AJAX.

You don't need Visual Studio to compile C# applications. You can just use the .NET Framework's command prompt, or better yet, Visual Studio Express. You can download it for free at http://msdn2.microsoft.com/en-us/express/default.aspx

by Kahey on Friday, November 2nd 2007 at 02:18 AM

Thanks Andrei.
I'm trying to keep everything browser-based and non-intrusive (ie: no need for customers to download anything at all) which is another reason for this project being php/mysql, html/javascript.

I've had a look at VSE now. I think I'll step up my learning curve into C# etc next project in 2008.

For now do you know where I could find a tutorial as good as yours for using PHP and JavaScript together to create a chat using AJAX?

Any help is always greatly appreciated,
Kahey

by D on Friday, November 30th 2007 at 06:54 PM

I have a question. I get an error when coming to the

if (ConResponse[0] == \'1\').

It says that Object reference not set to an instance of an object. How would I fix this?

by Martin on Monday, December 10th 2007 at 09:29 PM

I've been fiddling with this tutorial for weeks and even my courageous & endless searching of Google has failed to turn any results. Sadly to say, this tutorial is either complete crap, or is severely out-of-date. Every little bit of it (even if you were to copy & paste it from the pages, which I tried after having manually typed out all of the code) gets nit-picked by VC# Express, and there's nothing but errors left & right.

The biggest problem is the ConResponse[0] null object reference exception... but to me, logically speaking, the code looks complete... & I fail to see how the string ConResponse has not been instantiated either... and this appeared to be the best & most intuitive C# tutorial on the net... in fact it was, all other C# sites are pure rubbish... I guess C# is no territory for a Python & PHP programmer... I hope fewer people will throw caution to the wind when writing tutorials from now on...

by Andrei Pociu on Monday, December 10th 2007 at 10:14 PM

Martin, I believe you are moving into a topic to advanced for your knowledge of C#. While this tutorial is nowhere near the advanced level, you need to have at least a basic understanding of the language.

For example you pointed out that ConResponse is not getting instantiated. If you look above in the tutorial you will see:

string ConResponse = srReceiver.ReadLine();

If ConResponse[0] is null, your client is not receiving a message from the server. There\'s a multitude of reasons why this might be, some unrelated to the code. If you place breakpoints in the code and monitor the value of the objects you should easily be able to pinpoint the exact problem.

I haven\'t used VC# Express but it shouldn\'t make any difference.

by Martin on Wednesday, December 12th 2007 at 07:56 PM

I think I get it now. I wasn't assuming that VC#'s debugging was telling me that the code itself was semantically wrong, but after more testing this morning I realized what you've explained to me here. So, I'll simply need to do some troubleshooting with my network. Sorry for my harsh generalization. I'm just having a frustrated time moving into the world of languages like C#. I think it may be a wise bet for me to drop back to some even simpler tutorials, although to be honest... I think most of the basic tutorials I've found have been dull, unintuitive, and haven't really taught me much. Oh well, thanks again and sorry for leaking my frustration here.

by Rami on Monday, January 14th 2008 at 11:18 AM

Really it's a good work and explaniation....but pls can you describe how to make chat rooms...at least the idea not the code!!!!!

by Ben on Tuesday, January 15th 2008 at 08:07 AM

Thanks alot for all the tutorials, its help me learn alot about C# and understand the difference from php which is where i am from :)

But for some reason the chat client doesn\'t but i have a fealing its not the code itself, but something wrong with my machine. When ever i try and use the TcpClient class it seems to kill my application.

Any ideas on what could be causing this? or is it back to google for me? I am using the asp.net 3.0 framework.

by Steve on Saturday, January 19th 2008 at 11:32 PM

Why is it when I disconnect with the client it always errors out?
The debugger points me to this part of the code:
while (Connected)
{
// Show the messages in the log TextBox
this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { srReceiver.ReadLine() });
}

It's as if the connection is shutting down and this part of the code is still trying to read incoming lines from the server.

by john on Friday, February 1st 2008 at 04:53 AM

hi I had some error wen i tried to run both of them in my network can some one recomend a good c# book for this kind of advanced projects? thanks ;)

by Owen on Monday, February 11th 2008 at 01:48 PM

hi a book named 'beggining C#' might help you with it.

my question is do you have to make the server or does it tell you in this artical ? because i'am confused :P

by Bob on Saturday, February 23rd 2008 at 10:12 AM

This is wonderful! Only when i disconnect i get some error:

{
// Show the messages in the log TextBox
this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { srReceiver.ReadLine() });

}

This should be fixed but i dont know :(...and when you disconnect it should work but it didnt.

Also i am dieing to know how you make a userlist so you can see who is online and a private message system. Can you please make a tutor or add to this tutor how to make userlist and when u single click on it and than click on a button private message that u can send private messages to the user u want. Please can you make that!

thanks man! Andrei Pociu

by kenix on Tuesday, February 26th 2008 at 08:19 PM

the server application could be transformed into a service so that it runs in the background

Good explanation. I had try it... it worked perfectly. By the way, the client application can be transform into window service so that it runs in the background? I wish to run the

i had tried it but failed. once i run the services for the client( server is on ), it return error at this part
UpdateLog("Connected Successfully!);

==> by original code is (Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { "Connected Successfully!" });) which is only use for the System.windows.form

so, when i build the service, it cant use it. so, i make it and direct call the UpdateLog() method.

As i search from net the Invoke() Method is executes a delegate/represent on the thread that owns the controls underlying window handle. SO, it is related to the thread that i can not direct call the UpdateLog() method and need some code to refresh/ handle the thread ?

any solution or comment on it ?

thanks in advance
- kenix

by wisam91 on Tuesday, March 25th 2008 at 07:45 PM

thanks so much..really helpful!
but any one can give me the code to make a list that shows all user in the room?
& why there is some problems when trying the program in the local network..when it's connected it can only send 1 message then it crashes...
help me with that please

contact me at xiiv@live.com
thx and sorry for my english
peace

by Thiago Guerreiro on Tuesday, April 22nd 2008 at 09:27 PM

Wow...
Excellent Tutorial.

The best i find about Chat networking.

Thankz a lot and sorry 4 bad english =P

by Bhargavi on Saturday, May 24th 2008 at 02:57 AM

i want this chat application modified so that when 2 users chat the 3rd person who has joined the chat should not be able to see the message

by Jesse on Monday, May 26th 2008 at 03:53 PM

Nice tutorial. It is difficult to find information about .net sockets that work in a useful way.

by cmaye on Friday, August 8th 2008 at 03:55 AM

wow..excellent tutorial..thanks you so much..it 's really helpful to me. I would like to know private message system..like gtalk..u can see users who is online in ur contact list. when single click the contact, private message form will appear and can chat with him.How to send private message to one who is in ur contact list and how to transfer file to him..If you dont mind, can you make for me ...it is really important for me..i'm looking forward to ur mail..

my mail address is- cmaye59@gmail.com

by rajasekar.r on Monday, September 1st 2008 at 07:59 AM

i want clear tutorial in client and sever....

by spots on Tuesday, September 2nd 2008 at 06:40 PM

Hi,

Good tutorial! I was wondering if anybody can tell me where can I find a tutorial for connecting a chat client to a website? I'm new to programming and I'd like to make my own chat client for this website. I'd like to make a chat client like the ones they use for yahoo, but I don't want it for yahoo, I need it for this other web site. I've been searching in google, but all I can find is tutorials about client/server chat programs within a network. I know it involves protocols and other staff, but I'd like to know from scratch how to make a chat client.

Thank you.

by vineet on Saturday, September 13th 2008 at 04:40 AM

god bless you..

by sameh on Saturday, September 20th 2008 at 12:50 PM

hiiiiiiiiiiiiii

by csharper on Tuesday, September 23rd 2008 at 12:27 PM

cool, bro! thanks!

by Kalle on Friday, November 28th 2008 at 03:11 PM

I get this error when I tried to start the program:

"Error 1 'System.Windows.Forms.ListBox' does not contain a definition for 'AppendText' and no extension method 'AppendText' accepting a first argument of type 'System.Windows.Forms.ListBox' could be found (are you missing a using directive or an assembly reference?) C:\Documents and Settings\Urken\Mina dokument\Visual Studio 2008\Projects\Chat client\Chat client\Form1.cs 185 20 Chat client"

I have no idea what the problem is, since I'm totally new at this. I'd really appreciate some answers!

by Bruno @ Artesis Highschool on Tuesday, December 30th 2008 at 03:47 PM

hi fellow coders

solution to the disconnect / app close problem:

instead of the given .close() statements use these:

Connected = false;
srReceiver.Close();
srReceiver.Dispose();
thrMessaging.Abort();
swSender.Close();
swSender.Dispose();
tcpServer.Close();

paste them in both locations (close-conn and app-exit)

enjoy :)

by Casper on Saturday, January 3rd 2009 at 08:10 AM

Bruno, you rellay dont need to dispose the objects

The only problem with the disconnect thing is that the application is still listening for messages.

The only line you need to add is:
thrMessaging.Abort();

I added it in the CloseConnection method

by Manzoor Ahmed on Friday, January 23rd 2009 at 09:20 AM

What do I need to chat with someone over the Internet?

What IP address do I have to provide the other person to connect to me?

Does this program supports it?

by Vincent Bui on Wednesday, January 28th 2009 at 05:27 PM

Hey there, this looks like an excellent program, since I'm pretty new to C# though I am having some problems compiling it in the first place. It has nothing to do with not having a server, perhaps my code is off, but when it comes to ReadLine() and KeyChar, my library does not seem to have those functions. I am also using Visual Studio 2005

by Manzoor Ahmed on Thursday, January 29th 2009 at 04:39 AM

well, you shall download the projects.

First compile the server, and run it, then after that run the chat client.

by Asankalakmal on Thursday, January 29th 2009 at 11:56 PM

nice project,, Thanks.

by Saravana kumaran.T on Wednesday, February 25th 2009 at 02:05 AM

I have worked out with your client server project How to send the message from server to client?

by mohammad on Monday, March 9th 2009 at 03:18 AM

this codes help me so much thx a lot !!!!!

by mohammad on Monday, March 9th 2009 at 03:18 AM

this codes help me so much thx a lot !!!!!

by vhk on Wednesday, March 11th 2009 at 05:00 PM

hey, nice project! real nice.
But how about streaming class objects (like clsPerson)? Can u update this project, so we can send objects or images and documents too ?
I think its with networkstream and streaming byte arrays true the socket. But i dont really know how.
greetz

by John on Friday, March 27th 2009 at 03:19 PM

This is very cool. I am new this type of programming but this provides a great starting point.

Though when I try to connect though using the chat client, I get the following message for this line of code

tcpServer.Connect(ipAddr, 1986);

Socket Exception was unhandled
No connection could be made because the target machine actively refused it.

How do I fix this?

Thanks

by Duff on Sunday, April 12th 2009 at 05:37 AM

Great Project,but I have a problem I cant seem to get it to work over the Internet.Works great over a network ,but nothing happens if i Try it over the internet.Trying to start a simple internet chat with my friends

Please help!

by Joshua on Monday, April 13th 2009 at 06:02 PM

Can you send me the Scorces code and a project of this.

I do not understand how to exspalned the. tut. Send it to Chat_Ghosty@yahoo.com

by Mika on Monday, April 20th 2009 at 08:49 AM

Hi!
Can you send me your project, please...
My email is:
mikakbtu@gmail.com

by Mika on Monday, April 20th 2009 at 09:15 AM

Hi!
Can you send me your project, please...
My email is:
mikakbtu@gmail.com

by Adzie on Wednesday, May 20th 2009 at 12:49 PM

Hi, is it possible to display the users logged in in a list to the right of the chat box and how would you go about establishing this?

by rosy on Friday, May 22nd 2009 at 05:20 AM

Hi andrew,this code is really very helpful!!!
it helped me understand socket programming and build up my knowledge of it...
Thanks

by Demas on Tuesday, May 26th 2009 at 02:49 PM

I think C# is a hard code to learn

by Hadejia on Monday, June 1st 2009 at 08:53 AM

can u send me this project pls? i need your help
my email hadejia2000@gmail.com

by induduzo on Thursday, June 4th 2009 at 05:56 AM

Hey guys thanks for such greate exhibition.

hey Demas neva say neva bra C# is the best and easy to learn try java syntax its the same shit!!!

by gal on Saturday, June 27th 2009 at 01:21 PM

Hello,
I have a problen when i run the client application,
i recive the following error:

"System.NullReferenceException was unhandled"

on - if (ConResponse[0] == '1')

Can someone help me???

by j on Saturday, June 27th 2009 at 01:53 PM

by Lorenz on Thursday, July 2nd 2009 at 06:31 AM

How do you make different rooms?

by ATC on Wednesday, July 29th 2009 at 04:30 AM

Converted this project over the VC# 2008. Compiled with no errors, so the code is fine guys. As mentioned above, there IS an issue with the loop that listens for messages. I'm about to try the simple solution mentioned above. Also, the ChatServer application doesn't close when you hit the "X". I'm going to fix that.

You guys also need to make sure your firewall is NOT blocking this application. You might have to manually make an exception for your firewall and open port 1986 (the author's birth-year I bet =], heheh). Google it. There are free programs that can do this automatically as well. A little research can work wonders, lol. It's always disappointing to me when folks ask questions they could easily find answers to with Bing or Google.

Well, I'm about to fix these errors, and then work on this thing. I'm going to turn it into a high quality application with file sharing, private messaging, an intuitive GUI, and possibly even an auto-port manager. Also going to add some goodies, like buttons to clear history, save chat logs, etc (maybe even HTML support and ability to embed youtube videos). The log-in panel also needs to be on a new form, to have a more professional look. You could even create your own server where users register and have to login with a password.

This is a great starting point though. I'm experienced with programming (C/C ) and scripting (Lite-C), but fairly new to C# itself and networking. It's been a great intro, and I thank the author. Our team needs a solid chat/file share app for communication and file transfer, and this has me half way there. And this has also immensely helped me understand our engine's networking features and API that's integrated with VC#. Thanks again! =]

by saqib on Thursday, July 30th 2009 at 01:33 PM

Hi, I am trying to build a server-less chatting application in c# please can u tell me what should i do?

Any help is appriciated

Best regards

by saqib on Thursday, July 30th 2009 at 01:38 PM

Hi, I am trying to build a server-less chatting application in c# please can u tell me what should i do?

Any help is appriciated

Best regards

by abdullah on Monday, August 3rd 2009 at 11:12 PM

Hi, I'm also trying to build a standalone chatting application like YPress Chat application. Means that how I should implement server and client in a single application? Please help me I unable to find such an example, still I'm searching. Kindly give me the idea!

by abdullah on Monday, August 3rd 2009 at 11:13 PM

by kathirvel on Monday, August 31st 2009 at 06:22 AM

drop me a mail we can collabrate ourself and find the extreme inclusive of desktop sharing and live video conferencing.take a look at samples here http://kathirvelmariappan.blogspot.com
go to - video streaming

kathirvel.mariappan@gmail.com

by Jose Manuel on Monday, September 28th 2009 at 07:17 AM

I think there is a problem when the server is stoped during a tcpclient connection.

perhaps this code can be a solution, but not 100% tested:

private void ReceiveMessages()
{

srReceiver = new StreamReader(tcpServer.GetStream());
string ConResponse = srReceiver.ReadLine();

if (ConResponse[0] == '1')
{
this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { "Connected Successfully!" });
}
else
{
string Reason = "Not Connected: ";
Reason = ConResponse.Substring(2, ConResponse.Length - 2);
this.Invoke(new CloseConnectionCallback(this.CloseConnection), new object[] { Reason });
return;
}
string lineas;

// if server is connected a new line from srReceiver must be null diferent
while ((lineas=srReceiver.ReadLine())!=null

by jose manuel on Monday, September 28th 2009 at 07:21 AM

Sorry but previous comment was trimed perhaps because it's too long...

private void ReceiveMessages()
{

srReceiver = new StreamReader(tcpServer.GetStream());
string ConResponse = srReceiver.ReadLine();

if (ConResponse[0] == '1')
{
this.Invoke(new cargaCanalesCallback(this.cargaCanales));
this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { "Connected Successfully!" ConResponse.Substring(2, ConResponse.Length - 2)});
}
else
{
string Reason = "Not Connected: ";
Reason = ConResponse.Substring(2, ConResponse.Length - 2);
this.Invoke(new CloseConnectionCallback(this.CloseConnection), new object[] { Reason });
return;
}
string lineas;
while ((lineas=srReceiver.ReadLine())!=null

by Jose Manuel on Monday, September 28th 2009 at 07:23 AM

Impossible to post code modification comment, sorry me...

by mita on Thursday, October 1st 2009 at 11:57 PM

the tutorial was very helpful learning me C# as i am a beginner.But i had a problem i got an error saying

I am using visual studio 2008
Socket connection unhandled
No connection could be made because the target machine actively refused it ipaddress:1986
can you help me..

by Sibi on Thursday, October 8th 2009 at 02:11 AM

Excellent Tutorial....

by aziz on Thursday, October 22nd 2009 at 06:15 AM

by ATC on Monday, October 26th 2009 at 02:39 PM

But anyway, about the article. Interesting that the author took this route. Personally, I prefer asynchronous methods, which are much more convenient. The threading is basically handled "OS Level" by the CLR. Unless you're the type of person who wants 100% control over 100% of your execution (which is usually bug prone), that's what I'd recommend. And if you are that sort of person, you'd probably prefer unmanaged C/C anyway. ;)

I also thought using streams was a cool idea. I like to use byte[]s to handle this, but streams are certainly a valid concept. That might even work well for sending compressed files. I might experiment with that. I'm working on a full-blown network app right now, featuring chat, file sharing, a secure record/document database, and a lot more. It's in prototyping stages right now, but is already making life easier for all of us here at the office, and at home. This two year old article was one of my early inspirations. I just decided to revisit it, and pay homage to the author! Well done!

For those of you who want to take this further, look into asynchronous socket communication, and work on a fully featured, robust application with multiple classes and forms. Learning about delegates and how threading works is the most important thing, since the Sockets API is pretty easy to use. Also, for updating the UI, I feel a method like this is much more fluid and elegant (and it is also asynchronous):

public void Example(string username)
{
MethodInvoker calluithread = delegate
{ DoSomethingonUIThread(username); };

this.BeginInvoke(calluithread);
}

That's a thread safe call to update the UI, and inside the {} block, you can call any method on the UI's thread. You would want to call the Example() or similar method by a static delegate if it's in a different class than your server logic (like mine is). Otherwise, you'll be forced to call it on another instance of the form, which won't appear to do anything. I work hard to decouple the UI and other classes from each other. It makes code cleanup and fixes much easier, since classes don't depend on each other. A delegate doesn't really care what it's purpose is, as long as it's signature matches the target. ;)

Also, I remember the first time I played with the code here, there was a problem where the sockets didn't actually close. You have to decide what to do with them. If you simply want to disconnect, and then reconnect later (without closing the app), you need to call Close() on ALL of the open sockets. If you ARE closing the application, then I recommend Dispose(), as another person said. Why? You just don't need those resources any more! :) So just toss them. You know for sure it's dead. No sense in having sockets left open by mistake. So just kill them all (and make sure you get all of em, which may require you to iterate through an array or collection of them depending on your app). Even with C#, you can still manipulate the way objects are disposed of. You can even use finalizer methods which kick off when the GC disposes of something. But be cautious. Don't play with such methods unless you know what you're doing and have a good reason to do it in the first place.

by ATC on Wednesday, November 4th 2009 at 08:26 AM

Oops! I wrote two (maybe more, lol) mistakes in my post. The first was silly, I wrote "C/C" instead of "C/C ", as if C is different from C, haha! :)

Secondly, you DON'T call Dispose() on the sockets. The Sockets API has different means of doing so:

Synchronous:
Disconnect() - Disconnects, but saves resources...
Close() - Disconnects and destroys resources...

Asynchronous:
BeginDisconnect
EndDisconnect - Same as Disconnect, but async...

Sorry! :)

by Casper on Wednesday, December 2nd 2009 at 03:52 AM

Is there a reason why your not using UpdateLog("Connected Successfully!") instet of this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { "Connected Successfully!" });?

by User on Sunday, December 13th 2009 at 09:50 AM

Simple!

while (Connected)
{
if (srReceiver != null) // !!!!!!
{
// Show the messages in the log TextBox
this.Invoke(...);
}
}

by Jason on Monday, December 21st 2009 at 09:18 AM

May i know why i receive an error "No Connection could be made because the target machine actively refused it"

Thanks

by Jason on Monday, December 21st 2009 at 09:35 AM

The above problem is solved. But may i know if it is possible for me to communicate with someone of different IP though he is the server whereas i am the client.

Sorry for poor english

by Jason on Monday, December 21st 2009 at 09:35 AM

The above problem is solved. But may i know if it is possible for me to communicate with someone of different IP though he is the server whereas i am the client.

Sorry for poor english

by Shoot on Wednesday, December 23rd 2009 at 08:24 PM

How would I go about sending the userlist to the client?

by Aman patial on Wednesday, December 30th 2009 at 01:57 AM

Will we are able to communicate over diffrent LAN network with differnt IP range using this code.Where server is hosted on one LAN and client on different lan which is geographically sperate.

by Aman patial on Wednesday, December 30th 2009 at 01:57 AM

Will we are able to communicate over diffrent LAN network with differnt IP range using this code.Where server is hosted on one LAN and client on different lan which is geographically sperate.

by Aman patial on Wednesday, December 30th 2009 at 01:57 AM

Will we are able to communicate over diffrent LAN network with differnt IP range using this code.Where server is hosted on one LAN and client on different lan which is geographically sperate.

by Jasmine on Tuesday, February 9th 2010 at 08:20 AM

Hey Andrew the app works great.However the application shows a group chat.

by Berko Szabolcs on Thursday, March 18th 2010 at 02:34 PM

hey! thx a lot for this tut!!
Very great and helpfull!
But i find one problem. When i close ChatServer.exe,the program is running more in processes...

Sorry for my bad english.

Again, thx a lot ! :)

by Harsh on Tuesday, March 23rd 2010 at 06:59 AM

I don't understand why U ppl are still posting comments and asking doubts, This is very old post and Andrew might be dead by now...

by Valentin on Sunday, April 18th 2010 at 02:14 PM

For those that are having problems with the ENTER return key.. here is the solution

Put this line into method

public void InitializeConnection()
{
this.txtMessage.KeyPress = new KeyPressEventHandler(txtMessage_KeyPress);

...
}

private void txtMessage_KeyPress(object sender, KeyPressEventArgs e)
{
// If the key is Enter
if (e.KeyChar == 13)
{
SendMessage();
}
}

Valentin

by sketch on Monday, April 19th 2010 at 12:47 AM

can sum1 do a vid on how to do this plz

by Snaffi on Friday, April 23rd 2010 at 09:36 AM

Harsh is a legend

by Rakesh Ranjan on Saturday, April 24th 2010 at 10:45 AM

Hi..Thanks for this code.
After implementing this code I face a problem that
the "Enter" key is functioning first time. and after that it is not functioning.

Can any body help me in this ....

by Valentin on Saturday, April 24th 2010 at 01:48 PM

@Rakesh Rajan

Try to cast to char

public void InitializeConnection()
{
this.txtMessage.KeyPress = new KeyPressEventHandler(txtMessage_KeyPress);

...
}

private void txtMessage_KeyPress(object sender, KeyPressEventArgs e)
{
// If the key is Enter
if (e.KeyChar == (char)13)
{
SendMessage();
}
}

Hope it makes any difference

by Mika on Sunday, April 25th 2010 at 02:54 AM

thanks

by Rakesh Ranjan on Monday, April 26th 2010 at 03:34 AM

@Valentin
Thanks for your help.
I tried this code in my application but still it is arries the same problem.
after execution when i am sening message on "ButtonClick" it is working properly but when i am pressing the "Enter" key it is working first time and after that when i am writting the message and pressing the "Enter" key once again it makes the textBox blank.
After putting breakpoint i saw. the execution stops after calling the sendMessage() method.
That means it is not going to the thread for calling UpdateLog().

by Valentin on Monday, April 26th 2010 at 09:32 AM

@Rakesh

Look at this method. You shoold append the plus sign ( ) in front of = new KeyPres...

The form formats the = new Key.. so it is not showing the sign.

public void InitializeConnection()
{
this.txtMessage.KeyPress = new KeyPressEventHandler(txtMessage_KeyPress);

...
}

= should be written one after the other.

If it does not work it would be very strange because it works here.

by Valentin on Monday, April 26th 2010 at 09:36 AM

public void InitializeConnection()
{
this.txtMessage.KeyPress PLUS= new KeyPressEventHandler(txtMessage_KeyPress);

...
}

by Rakesh Ranjan on Thursday, May 6th 2010 at 12:54 AM

@valentin
Thanks for the help.
Your code is working.But one problem I am facing, When i am making the textMessageBox(i.e. where we are writing the message) single line , it is working But when i am changing it to multiple lines ,it is not working. the crussor is comming to second line after the keypress event.

But i want to make the textMessageBox to multiple lines.
Can u help me in this plz....

Thanks.

by Rakesh Ranjan on Wednesday, May 12th 2010 at 01:52 AM

hello everybody..
In this application I want to put the port number dynamically on which it is currently running.
So i want know, how i will get the port number programetically at runtime in the application..

can any body help me....
Thanks.

by Igor on Tuesday, May 25th 2010 at 06:22 PM

Hi! I'm having a trouble. When i'm disconnnection a client with button i'm getting an IOException 10004:
Unable to read data from a transport connection
A blocking operation was interrupted by a call to WSACancelBlockingCall

in a while cicle in ReceiveMessages() function

while (Connected)
{
// Show the messages in the log TextBox
this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] { srReceiver.ReadLine() });

}

It looks like it still trying to get message when Sender, Receiver and Server are already closed. Maybe it's because it was already in the while when Connected become false and those were closed.

by Igor on Tuesday, May 25th 2010 at 06:36 PM

It happens even when i'm closing a client.Oh, and i'm using a VisualStudio2008

by eduardo on Wednesday, June 2nd 2010 at 02:17 PM

hi. . .u application is perfect 4me. . but my teacher want it is a conversation private... As the chat. . .First where it is a room and of there it is privately. . . .pd....soy de mexico. . .

by Fabrizio on Friday, June 11th 2010 at 07:20 PM

This is AWESOME worked like a charm and easy to understand, at least if you know c#. I always wanted to know how to do network apps and I didn't know how so this helped me a lot.
Thank you so much you made a man happy

by BlackCheetah on Sunday, June 13th 2010 at 07:52 PM

You saved me!

Can repay you with

Dinner!

This is what true warriors strive for!

by synesthesis on Friday, June 25th 2010 at 03:02 AM

great! I also make some tutorials in my web page I have to admit that this is well explained and time dedicated not like others where you finally get confused. I appreciate your work.
Thank you.

by sadegh on Friday, July 2nd 2010 at 02:14 AM

by sadegh on Friday, July 2nd 2010 at 02:17 AM

hi, thanks for great app

but i have one problem: my computer configured to have automatically ip address and when i use ipconfig /all command that shows something like below:

Windows IP Configuration

PPP adapter Broadband Connection:

Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 95.38.95.204
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . : 0.0.0.0

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::64d7:e4ee:ba7e:1ede
IPv4 Address. . . . . . . . . . . : 192.168.72.198
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1

i should use 95.38.95.204 or 192.168.72.198 as ip address for server and client?

when i use 192.168.72.198, server connect successfully but client throw an SocketException like below:

also when i use 127.0.0.1 for both server and client, both works correctly.

thanks if anybody can help me

by sadegh on Friday, July 2nd 2010 at 02:18 AM

hi, thanks for great app

but i have one problem: my computer configured to have automatically ip address and when i use ipconfig /all command that shows something like below:

Windows IP Configuration

PPP adapter Broadband Connection:

Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 95.38.95.204
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . : 0.0.0.0

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::64d7:e4ee:ba7e:1ede
IPv4 Address. . . . . . . . . . . : 192.168.72.198
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1

i should use 95.38.95.204 or 192.168.72.198 as ip address for server and client?

when i use 192.168.72.198, server connect successfully but client throw an SocketException like below:

A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 192.168.72.198:1986

also when i use 127.0.0.1 for both server and client, both works correctly.

thanks if anybody can help me

by Valentin on Friday, July 2nd 2010 at 08:34 AM

you should use NAT to make connections possible from outside.
Your LAN IP should remain like: 192.168.x.x

your WAN IP is like: 88.22.43.121 (example)

When people from outside try to connect to 88.22.43.121 your NAT should forward the trafic to your LAN IP which in this example is 192.168.x.x

Hope this clear things up

by Sadegh on Friday, July 2nd 2010 at 12:26 PM

thanks Valentin but i want to connect as local no outside

by Someone on Sunday, July 11th 2010 at 03:39 AM

Then just use Valentin's example of the LAN IP adress since it is local. Anyway vary nice application Thanks.

by Dimple on Wednesday, July 14th 2010 at 06:37 AM

i am new to asp.net and c#.but your tutorial was really helpful and easy to understand.i tried to implement this in my web based application.but facing some problems.can you suggest what changes i need to make while implementing it in web based.
the error was.."this.invoke is not recognized"

by Dimple on Thursday, July 15th 2010 at 12:21 AM

by Mattias on Wednesday, July 28th 2010 at 01:30 PM

Cant find the text message box in my tools :(
Witch one you called txtLog!!! :( What is the name of it in the toolbox?! Plz tell me! :)

by Dimple on Thursday, July 29th 2010 at 03:55 AM

i want to convert this application to a web based client..everything is working..but since control.invoke function is not in system.web therefore it is giving errors..is there any alternative for using this.invoke???please help me..

by Dimple on Thursday, July 29th 2010 at 03:56 AM

by Valentin on Thursday, July 29th 2010 at 10:18 AM

No need for 100 posts!

by STSccc on Friday, July 30th 2010 at 12:41 AM

i want study C# programing language

by STSccc on Friday, July 30th 2010 at 12:41 AM

i want study C# programing language

by STSccc on Friday, July 30th 2010 at 12:41 AM

i want study C# programing language

by STSccc on Friday, July 30th 2010 at 12:41 AM

i want study C# programing language

by dries hoebeke on Saturday, July 31st 2010 at 06:00 AM

This is an awesome tutorial. Thanks a lot for posting it!

by AEHP on Friday, August 6th 2010 at 05:34 AM

Excelent work!!!

I changed the order of lines and it runs perfectly:

Connected.Close();
thrMessaging.Abort();

swReceiver.Close();
swSender.Close();
tcpServer.Close();

Thank at lot.

by AEHP on Friday, August 6th 2010 at 05:34 AM

Excelent work!!!

I changed the order of lines and it runs perfectly:

Connected.Close();
thrMessaging.Abort();

swReceiver.Close();
swSender.Close();
tcpServer.Close();

Thank at lot.

by Muhammad Assam on Tuesday, August 10th 2010 at 05:28 AM

hi >>>>.can any one help me to become a C# professional >>..send me the books so i follow nd sites having meterial that can help mew>>.i will bwe very thankfulllllllll plzzzz>>.

by Muhammad Assam on Tuesday, August 10th 2010 at 05:28 AM

hi >>>>.can any one help me to become a C# professional >>..send me the books so i follow nd sites having meterial that can help mew>>.i will bwe very thankfulllllllll plzzzz>>.

by Muhammad Assam on Tuesday, August 10th 2010 at 05:28 AM

hi >>>>.can any one help me to become a C# professional >>..send me the books so i follow nd sites having meterial that can help mew>>.i will bwe very thankfulllllllll plzzzz>>.

by Muhammad Assam on Tuesday, August 10th 2010 at 05:28 AM

hi >>>>.can any one help me to become a C# professional >>..send me the books so i follow nd sites having meterial that can help mew>>.i will bwe very thankfulllllllll plzzzz>>.

by Muhammad Assam on Tuesday, August 10th 2010 at 05:29 AM