Simple Messenger - A C# MSN Messenger-like Chat Application

Introduction

This is a simple MSN Messenger like chat application using socket programming. It allows the users to send and receive messages by running two Simple Messengers.
You can read this article from my blog: http://hantou.blogspot.com/.

There are two specific features other than the regular MSN Messenger:

'Hex'

TRUE: The data will be displayed in Hex format.
FALSE: The data will be displayed in regular text.

'No print on receiving'

TRUE: The received data will not be printed on the textbox.
FALSE: The received data will be printed on the textbox.

Background

One day when I was working on socket programming, I needed to monitor data transmission. Although Visual Studio already has a debugger for the user to monitor the data, I still needed a third application to cache the data and take a look at it. This comes with the idea for the Simple Messenger. You can use this program as a chat application when you run two simple Messengers. If you connect your computer to a device, another software, a web application, etc., you will be able to send/receive data via one Simple Messenger application. In my case, I just connect my computer to a device which has Ethernet connection and I need to monitor the data sent by the device during the run time. The main purpose of this article here is to share this program with you regarding socket programming and multiple threads.

KeyValuePair

A helper class wraps a Socket and a byte array.

Collapse

public class KeyValuePair
{
public Socket socket;
public byte[] dataBuffer = new byte[1];
}

Overview

There are two main classes named Server.cs and Client.cs standing for Server mode and Client mode respectively. Note, the scenario is that only one server and one client are connected. This means that if you try to open one server and multiple clients then I cannot promise anything. The one-to-many case is not implemented and this is beyond the main issue that is being discussed here.

Connection

The connection is slightly different between the Server Mode and the Client Mode.

First look at the Server Mode:

Collapse

public void Connect(string ipAddr, string port)
{
server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipLocal = new IPEndPoint(IPAddress.Any, Convert.ToInt32(port));
server.Bind(ipLocal);//bind to the local IP Address...
server.Listen(5);//start listening...

// create the call back for any client connections...
server.BeginAccept(new AsyncCallback(OnClientConnect), null);
}

The server needs to watch for the connection to see if there is any client trying to connect to it.

Collapse

public void OnClientConnect(IAsyncResult asyn)
{
try
{
if (server != null)
{
   tempSocket = server.EndAccept(asyn);
   WaitForData(tempSocket);
   server.BeginAccept(new AsyncCallback(OnClientConnect), null);
}
}
/* ... */
}

Before the server socket receives any data, we must prepare for it ahead. Here the KeyValuePair object is imported as a parameter.

Collapse

public void WaitForData(Socket soc)
{
try
{
if (asyncCallBack == null)
   asyncCallBack = new AsyncCallback(OnDataReceived);

KeyValuePair aKeyValuePair = new KeyValuePair();
aKeyValuePair.socket = soc;

// now start to listen for incoming data...
aKeyValuePair.dataBuffer = new byte[soc.ReceiveBufferSize];
soc.BeginReceive(aKeyValuePair.dataBuffer, 0, aKeyValuePair.dataBuffer.Length,
            SocketFlags.None, asyncCallBack, aKeyValuePair);
}
/* ... */
}

Now look at the Client Mode:

Collapse

public void Connect(string ipAddr, string port)
{
client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipe = new IPEndPoint(IPAddress.Parse(ipAddr), Convert.ToInt32(port));
client.Connect(ipe);

clientListener = new Thread(OnDataReceived);
isEndClientListener = false;
clientListener.Start();
}

Data Receive

Since the AsyncCallback is used for the server, receiving the data will be different.

For the Server Mode

Collapse

KeyValuePair aKeyValuePair = (KeyValuePair)asyn.AsyncState;
//end receive...
int iRx = 0;
iRx = aKeyValuePair.socket.EndReceive(asyn);
if (iRx != 0)
{
byte[] recv = aKeyValuePair.dataBuffer;
}

For the Client Mode

Collapse

byte[] recv = new byte[client.ReceiveBufferSize];  //you can define your own size
int iRx = client.Receive(recv );
if (iRx != 0)
{
//recv should contain the received data.
}

Data Send

Sending the data is as easy as calling the Send() method that comes with the Socket. E.g.

Collapse

soc.Send(dataBytes);//'soc' could either be the server or the client

Error Handling

In Server's receive block, you might want to handle the SocketException with ErrorCode == 10054. This error code indicates the connection reset for peers. Refer to MSDN.

Collapse

if (e.ErrorCode == 10054)//Connection reset, 
// http://msdn.microsoft.com/en-us/library/ms740668(VS.85).aspx
{
/* ... */
}

Points of Interest

Every time I used the MSN Messenger to chat with my friends, I was worried if my conversation would be recorded by 'MSN'. Now I'm happy and 'safe' to use my own chat application to chat with my friends, er... within a local network. However, the main benefit of this program is that I learned how to play with the Ethernet and sockets. I hope this will benefit you as well.

For more information about me, please visit my blog: hantou.blogspot.com.

History

2^nd July, 2008 - First version
16^th April, 2009 - Updated article downloads and images
20^th April, 2009 - Updated article

Hantou Software Development

Thursday, April 16, 2009