Question

I have been given a code that also involves an asynchronous socketing which I am begginer at. I do not know why the object state as a second parameter of BeginAccept socket is null and to be honest, I did not get the use of this parameter from MSDN. And also, why the BeginAccept is being called again from the callback method?

public void Start()
        {

                this.mTcpListener.Start();
                this.mTcpListener.BeginAcceptSocket(this.AcceptClient, null);
        }

 protected void AcceptClient(IAsyncResult ar)
        {
            if (this.mTcpListener != null)
            {
                System.Net.Sockets.Socket s = this.mTcpListener.EndAcceptSocket(ar);
                Client c = new Client(this, s, this.GetFreePlayerID());

                ..some code for adding the client instance to collection....                  
                this.mTcpListener.BeginAcceptSocket(this.AcceptClient, null);
            }
        }

Answer 1

Following on from fsimonazzi, I assume that this code is part of a server which is meant to hold many incoming connections.

BeginAccept is used to start the accept process on a socket.

In AcceptClient it then finishes the AcceptConnection async process with EndAcceptSocket.

At this point the program is no longer listening for new connections/sockets. In order to do that, it again starts an async BeginAcceptSocket process.