Socket Programming - Receive Buffer Length

[danomano]

The code below works fine. As of now I just set the buffer length real big and all is good. However, I hate the impreciseness of that.

So my question in general is how do I know what length to set the buffer? In specific, my question is what causes the 'completed' event in the OnSocketConnectCompleted method to fire? Does it fire at end of a packet or does happen at some end of data marker?

        public SocketClient(Page pg, Int32 port, Int32 length)
        {
            this.PAGE = pg;
            this.LENGTH = length;
            this.Q = new Queue<byte[]>();
 
            DnsEndPoint endPoint = new DnsEndPoint("111.222.333.444", port);
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
 
            SocketAsyncEventArgs argz = new SocketAsyncEventArgs();
            argz.UserToken = socket;
            argz.RemoteEndPoint = endPoint;
            argz.Completed += new EventHandler<SocketAsyncEventArgs>(OnSocketConnectCompleted);
            socket.ConnectAsync(argz);
        }
 
        private void OnSocketConnectCompleted(object sender, SocketAsyncEventArgs e)
        {
            byte[] response = new byte[this.LENGTH];
            e.SetBuffer(response, 0, response.Length);
            e.Completed += new EventHandler<SocketAsyncEventArgs>(OnSocketReceive);
            Socket socket = (Socket)e.UserToken;
            socket.ReceiveAsync(e);
        }
 
        private void OnSocketReceive(object sender, SocketAsyncEventArgs e)
        {
            Q.Enqueue(e.Buffer);
 
            //Prepare to receive more data
            Socket socket = (Socket)e.UserToken;
            byte[] response = new byte[this.LENGTH];
            e.SetBuffer(response, 0, response.Length);
            socket.ReceiveAsync(e);
        }

[Plater]

OnSocketConnectCompleted is fired when a connection is established. Data transfer has nothing to do with it

[danomano]

@Plater
Right but I did not ask anything about what causes the OnSocketConnectCompleted event to fire. Please reread the question, I asked "what causes the completed' event in the OnSocketConnectCompleted method to fire"

Obviously I am trying to understand how to adjust the incoming buffer to match the incoming data. Please explain the issue if you can. Could you possibly consider answering again?

I do appreciate the help.

[Plater]

@danomano
Edit: ok I see the subtle difference. We got so many people here where english is not their best language, that I just understood it to be a translation issue.

[Frinavale]

@danomano
The best way to do this would be to append the length of the data being sent to the beginning of the data being sent.

Add an Integer (or Int16 if you don't want to use the full 32) to the beginning of the data. Read this integer when you first receive a request and then adjust your buffer.

One thing that you should know is that the data being sent could contain data for more than one "thing" that you are sending over the socket.

In other words the data that you retrieve in your OnSocketConnectCompleted method could be for more than one "thing". You have to know how big the thing is that you're sending or else you won't know when the first thing has finished sending and the next thing begins (and of course you need to adjust your buffer size)

You can see the problems that I faced with this same issue in this thread: Determining the size of data being set from socket server

-Frinny