Question

So I’ve started to muck around with sockets and asynchronously reading from them.

First question is what is the difference between this:

socket.BeginReceive(readResult.Buffer, 0, SocketReadResult.BufferSize, 0, new AsyncCallback(ReadCallback), readResult);

and

socket.BeginReceive(readResult.Buffer, 0, SocketReadResult.BufferSize, 0, ReadCallback, readResult);

Also, given this as my callback function, why did the example I read have a try/catch around the whole thing, surely you only need a try/catch around the socket.EndReceive() call?

public void ReadCallback(IAsyncResult ar)
{
    try
    {
        var readResult = (SocketReadResult)ar.AsyncState;
        var socket = readResult.Socket;
        int bytesRead = socket.EndReceive(ar);

        if (bytesRead > 0)
        {
            // There might be more data, so store the data received so far.
            readResult.Text.Append(Encoding.ASCII.GetString(readResult.Buffer, 0, bytesRead));

            // Get the rest of the data.
            socket.BeginReceive(readResult.Buffer, 0, SocketReadResult.BufferSize, 0, new AsyncCallback(ReadCallback), readResult);
        }
        else
        {
            var newRead = new SocketReadResult(socket);

            socket.BeginReceive(readResult.Buffer, 0, SocketReadResult.BufferSize, 0, new AsyncCallback(ReadCallback), newRead);

            // All the data has arrived; put it in response.
            if (readResult.Text.Length > 1) ((IMessageSender)this).RouteMessage(this, new MessageString(readResult.Text.ToString()));
        }
    }
    catch (Exception e)
    {
        // TODO: manage this exception.
    }
}

public struct SocketReadResult
{
    StringBuilder Text;
    Socket Socket;
    byte[] Buffer;

    public const int BufferSize = 1024;

    public SocketReadResult(Socket s)
    {
        Socket = s;
        Buffer = new byte[BufferSize];
        Text = new StringBuilder();
    }
}

Last of all, should you wish to gracefully close the listener after you have called socket.BeginReceive(), what functions do you call and how is it managed?

Answer 1

socket.BeginReceive(readResult.Buffer, 0, SocketReadResult.BufferSize, 0, new AsyncCallback(ReadCallback), readResult);

and

socket.BeginReceive(readResult.Buffer, 0, SocketReadResult.BufferSize, 0, ReadCallback, readResult);

both are the same thing, its same thing as

        //both are the same thing
        button1.Click += new EventHandler(button1_Click);
        button1.Click += button1_Click;