TCP Communication-Asynchronous Read Loop doesn't end

Question

I am using Asynchronous TCP server/client communication. I have noticed in my log that the same client reconnects several times. However, it never shows that it was disconnected. My code has logging for both connection and disconnection. So why does readAsync stay in loop while the client has disconnected? Here is the code for your reference:

   private async Task Accept(TcpClient client)
    {
       //get client information 
        string clientEndPoint = GetClientIPAddress(client);          
        log.Info("Client connected at " + clientEndPoint); //same client is connected several times in log

        await Task.Yield (); 

        try 
        {              
            using (client) 
            using (NetworkStream stream = client.GetStream ()) 
            { 
                byte[] dataReceived = new byte [100];                  
                while (await stream.ReadAsync(dataReceived, 0, dataReceived.Length) != 0) //read input stream  -  0=>end of stream is reached
                {                    
                    //pass on data for processing                      
                    var task = ProcessData(dataReceived);   
                }                   
            }
            log.Info("Closing client connection " + clientEndPoint);//this line is never reached in log
            if (client.Connected)
                client.Close();
        } //end try
        catch (Exception ex) 
        {
            log.Error(ex.Message);
            log.Info("Closing client connection " + clientEndPoint);
            if (client.Connected)
                client.Close();
        }

Answer 1

It looks like you may have a half-open problem. You should periodically write data to determine whether the socket is still connected; reads can detect graceful shutdowns but not half-open scenarios.

I describe the half-open problem more on my blog.