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POC# Async Server/Client Architecture
 

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  1. POC# Async Server/Client Architecture
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    <p>first post ever on stack overflow!</p> <p>Anyway...I'm trying to teach myself networking programming in my spare time and I've reached a snag I just cant wrap my head around. After playing with synchronous networking methodology over a few days I decided to make a client/server program that could:</p> <ul> <li>Handle multiple concurrent connections</li> <li>Handle multiple streams of communication</li> <li>Have true two way communication</li> </ul> <p>On a more general level I want to make a chat program. Multiple client connections to a server that can send and receive data individually with no problems...but also have the server send data from each client to the others.</p> <p>Now I haven't gotten as far as I'd like to yet so I'm here for a little guidance. I can't seem to get my loops working properly and I'm sure it has to do with the asynchronous nature of the code...for whatever reason I just can't seem to figure out whats wrong. Here's the the blocks of code:</p> <p>Server.cs</p> <pre><code>using System; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; // State object for reading client data asynchronously public class StateObject { // Client socket. public Socket workSocket = null; // Size of receive buffer. public const int BufferSize = 1024; // Receive buffer. public byte[] buffer = new byte[BufferSize]; // Received data string. public StringBuilder sb = new StringBuilder(); } public class AsynchronousSocketListener { // Thread signal. public static ManualResetEvent allDone = new ManualResetEvent(false); public AsynchronousSocketListener() { } public static void StartListening() { // Data buffer for incoming data. byte[] bytes = new Byte[1024]; // Establish the local endpoint for the socket. // The DNS name of the computer // running the listener is "host.contoso.com". //IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName()); //IPAddress ipAddress = ipHostInfo.AddressList[0]; IPAddress ipAddress = System.Net.IPAddress.Loopback; IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 3000); // Create a TCP/IP socket. Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); // Bind the socket to the local endpoint and listen for incoming connections. try { listener.Bind(localEndPoint); listener.Listen(100); while (true) { // Set the event to nonsignaled state. allDone.Reset(); // Start an asynchronous socket to listen for connections. Console.WriteLine("Waiting for a connection..."); listener.BeginAccept( new AsyncCallback(AcceptCallback), listener); // Wait until a connection is made before continuing. allDone.WaitOne(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } Console.WriteLine("\nPress ENTER to continue..."); Console.Read(); } public static void AcceptCallback(IAsyncResult ar) { // Signal the main thread to continue. allDone.Set(); // Get the socket that handles the client request. Socket listener = (Socket)ar.AsyncState; Socket handler = listener.EndAccept(ar); // Create the state object. StateObject state = new StateObject(); state.workSocket = handler; handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state); } public static void ReadCallback(IAsyncResult ar) { String content = String.Empty; // Retrieve the state object and the handler socket // from the asynchronous state object. StateObject state = (StateObject)ar.AsyncState; Socket handler = state.workSocket; // Read data from the client socket. int bytesRead = handler.EndReceive(ar); if (bytesRead &gt; 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString( state.buffer, 0, bytesRead)); // Check for end-of-file tag. If it is not there, read // more data. content = state.sb.ToString(); if (content.IndexOf("&lt;EOF&gt;") &gt; -1) { // All the data has been read from the // client. Display it on the console. Console.WriteLine("Read {0} bytes from socket. \n Data : {1}", content.Length, content); // Echo the data back to the client. Send(handler, content); } else { // Not all data received. Get more. handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state); } } } private static void Send(Socket handler, String data) { // Convert the string data to byte data using ASCII encoding. byte[] byteData = Encoding.ASCII.GetBytes(data); // Begin sending the data to the remote device. handler.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendCallback), handler); } private static void SendCallback(IAsyncResult ar) { try { // Retrieve the socket from the state object. Socket handler = (Socket)ar.AsyncState; // Complete sending the data to the remote device. int bytesSent = handler.EndSend(ar); Console.WriteLine("Sent {0} bytes to client.", bytesSent); handler.Shutdown(SocketShutdown.Both); handler.Close(); } catch (Exception e) { Console.WriteLine(e.ToString()); } } public static int Main(String[] args) { StartListening(); return 0; } } </code></pre> <p>Client.cs</p> <pre><code>using System; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; public class StateObject { // Client socket. public Socket workSocket = null; // Size of receive buffer. public const int BufferSize = 256; // Receive buffer. public byte[] buffer = new byte[BufferSize]; // Received data string. public StringBuilder sb = new StringBuilder(); } public class Program { public static ManualResetEvent connectDone = new ManualResetEvent(false); public static ManualResetEvent sendDone = new ManualResetEvent(false); public static ManualResetEvent receiveDone = new ManualResetEvent(false); public static void Connect(EndPoint remoteEP, Socket client) { client.BeginConnect(remoteEP, new AsyncCallback(ConnectCallback), client); connectDone.WaitOne(); } private static void ConnectCallback(IAsyncResult ar) { try { // Retrieve the socket from the state object. Socket client = (Socket)ar.AsyncState; // Complete the connection. client.EndConnect(ar); Console.WriteLine("Socket connected to {0}", client.RemoteEndPoint.ToString()); // Signal that the connection has been made. connectDone.Set(); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void Send(Socket client, String data) { // Convert the string data to byte data using ASCII encoding. byte[] byteData = Encoding.ASCII.GetBytes(data); // Begin sending the data to the remote device. client.BeginSend(byteData, 0, byteData.Length, SocketFlags.None, new AsyncCallback(SendCallback), client); } private static void SendCallback(IAsyncResult ar) { try { // Retrieve the socket from the state object. Socket client = (Socket)ar.AsyncState; // Complete sending the data to the remote device. int bytesSent = client.EndSend(ar); Console.WriteLine("Sent {0} bytes to server.", bytesSent); // Signal that all bytes have been sent. sendDone.Set(); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void Receive(Socket client) { try { // Create the state object. StateObject state = new StateObject(); state.workSocket = client; // Begin receiving the data from the remote device. client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void ReceiveCallback(IAsyncResult ar) { try { // Retrieve the state object and the client socket // from the asynchronous state object. StateObject state = (StateObject)ar.AsyncState; Socket client = state.workSocket; // Read data from the remote device. int bytesRead = client.EndReceive(ar); if (bytesRead &gt; 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead)); // Get the rest of the data. client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state); } else { // All the data has arrived; put it in response. if (state.sb.Length &gt; 1) { string response = state.sb.ToString(); Console.WriteLine(response); } // Signal that all bytes have been received. receiveDone.Set(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } } static void Main(string[] args) { IPAddress ipAddress = System.Net.IPAddress.Loopback; IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 3000); Socket sock = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp); Connect(localEndPoint, sock); string packet; while (true) { packet = Console.ReadLine(); packet += "&lt;EOF&gt;"; Send(sock, packet); Receive(sock); connectDone.WaitOne(); } } } </code></pre>
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    1. COCould you perhaps explain in a bit more detail exactly _what's_ not working properly with your loops?
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    2. COAre you sure this isn't an assignment?
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