[SOLVED | C# | .NET 2.0] Issue with asynchronous socket I/O

[ingam0r]

Hi!
At the moment I am coding a little server-tool in C# using the .NET Framework 2.0. Everything works fine, but I encounter a very strange problem when packets for one connection are received nearly at the same time. When you look at the Connection-class you will see that I count the packets I received. When two packets are received nearly at the same time one of those packets gets ignored! It looks like it is never ever received by my server.

Okay. I found the solution myself. I was too stupid to think of TCP being a stream-oriented protocol. I always read the first packet in the buffer and didn't care of other packets that could have been in the buffer, too. Well... now it works ;)

This is the code where I start listening for incoming connections:

listener.Bind(localEndPoint);    // listener is my listen-socket
listener.Listen(5);        

while (true)
{
   allDone.Reset();
   Console.WriteLine("Waiting for connection...");
   listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
   allDone.WaitOne();
}

And here are my callbacks:

AcceptCallback(IAsyncResult ar)
{
   allDone.Set();
   Socket listener = (Socket)ar.AsyncState;
   Socket handler = listener.EndAccept(ar);

   Connection state = new Connection();
   state.ClientSocket = handler;
   state.Buffer = new byte[Connection.Buffersize];
   handler.BeginReceive(state.Buffer, 0, Connection.Buffersize, 0, 
      new AsyncCallback(ReadCallBack), state);
}

ReadCallback(IAsyncResult ar)
{
   Connection state = (Connection)ar.AsyncState;
   Socket handler = state.ClientSocket;
   int byteRead = handler.EndReceive(ar);

   if (byteRead > 0)
   {
      state.Process(state.Buffer);   // This call could take some time
   }
   handler.BeginReceive(state.Buffer, 0, 
   Connection.Buffersize, 0, new AsyncCallback(ReadCallBack), state);
}

The class Connection is the class that encapsulates the details for every connection. It looks like this (this is a shortened version):

class Connection
{
   public const int Buffersize = 1024;

   public int packetsreceived = 0;
   public Socket ClientSocket;
   public byte[] Buffer;

   public void Process(byte[] packetdata)
   {
      // Process the packet. Can take some time
   }
}

I hope you can help me. This is really annoying and it starts to piss me off :bad:

Thanks for you help.Cheers!:smilie_xp

[MentaL]