TCP async - sample for client and server

Markus Freitag 3,786 Reputation points
2021-06-18T11:10:03.193+00:00

Hello,

I am looking for a simple and good solution.
I still found this, looks good. It is a must with socket, because my customer use also a C# TCP connection.

How can I achieve that the server sends an event and the client then receives it and evaluates it, maybe answers it.

Moments the client closes the connection if nothing is present. Must not be.
See the comment

  // ###

I need an event receive. How can I achieve this?
6056200

// *** Server
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace MyTcpServer
{
    class Program
    {
        static int Main(string[] args)
        {
            try
            {
                StartListener(7001).Wait();
                return 0;
            }
            catch (Exception ex)
            {
                Console.Error.WriteLine(ex);
                return -1;
            }
        }

        private static async Task StartListener(int port)
        {
            var tcpListener = TcpListener.Create(port);
            tcpListener.Start();
            for (; ; )
            {
                Console.WriteLine("[Server] waiting for clients...");
                using (var tcpClient = await tcpListener.AcceptTcpClientAsync())
                {
                    try
                    {
                        Console.WriteLine("[Server] Client has connected");
                        using (var networkStream = tcpClient.GetStream())
                        using (var reader = new StreamReader(networkStream))
                        using (var writer = new StreamWriter(networkStream) { AutoFlush = true })
                        {
                            var buffer = new byte[4096];
                            Console.WriteLine("[Server] Reading from client");
                            var request = await reader.ReadLineAsync();
                            string.Format(string.Format("[Server] Client wrote '{0}'", request));

                            await writer.WriteLineAsync($"[Server] to Client {request}");
                            //for (int i = 0; i < 5; i++)
                            //{
                            //    await writer.WriteLineAsync("I am the server! HAHAHA!");
                            //    Console.WriteLine("[Server] Response has been written");
                            //    await Task.Delay(TimeSpan.FromSeconds(1));
                            //}
                        }
                    }
                    catch (Exception)
                    {
                        Console.WriteLine("[Server] client connection lost");
                    }
                }
            }
        }
    }
}








// *** CLIENT


using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace MyClient
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            Task _ = ConnectAsTcpClient("127.0.0.1", 7001);
        }

        private void OutputWriteLine(string text)
        {
            output.Text = output.Text + "\n" + text;
            output.ScrollToEnd();
        }


        private void btnSend_Click(object sender, RoutedEventArgs e)
        {
            OutputWriteLine("Button_Click Send");
            ClientRequestString = "Hello Mr. Server from Button";
        }

        private async Task ConnectAsTcpClient(string ip, int port)
        {
            for (; ; )
            {
                try
                {
                    await Task.Delay(millisecondsDelay: 5000);
                    using (var tcpClient = new TcpClient())
                    {
                        OutputWriteLine("[Client] Attempting connection to server " + ip + ":" + port);
                        Task connectTask = tcpClient.ConnectAsync(ip, port);
                        Task timeoutTask = Task.Delay(millisecondsDelay: 6100);
                        if (await Task.WhenAny(connectTask, timeoutTask) == timeoutTask)
                        {
                            throw new TimeoutException();
                        }


                        OutputWriteLine("[Client] Connected to server");
                        using (var networkStream = tcpClient.GetStream())
                        using (var reader = new StreamReader(networkStream))
                        using (var writer = new StreamWriter(networkStream) { AutoFlush = true })
                        {
                            OutputWriteLine(string.Format("[Client] Writing request '{0}'", ClientRequestString));
                            await writer.WriteLineAsync(ClientRequestString);

 // ### not good, server can send a event, at moment is closing the connection and reconnect.
 // ### I need a event, if new data available
 // ### How can I do it?
                            try
                            {
                                for (; ; )
                                {
                                    var response = await reader.ReadLineAsync();
                                    if (response == null)
                                    {
                                        break;
                                    }
                                    OutputWriteLine(string.Format("[Client] Server response was '{0}'", response));
                                }
                                OutputWriteLine("[Client] Server disconnected");
                            }
                            catch (IOException)
                            {
                                OutputWriteLine("[Client] Server disconnected");
                            }
                        }
                    }
                }
                catch (TimeoutException)
                {
                    // reconnect
                    OutputWriteLine("[Client] Timeout - No connection");
                }
            }
        }

        //private static readonly string ClientRequestString = "Hello Mr. Server";
        private string ClientRequestString = "Hello Mr. Server";


    }
}
C#
C#
An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
10,212 questions
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2 answers

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  1. AgaveJoe 26,191 Reputation points
    2021-06-18T19:30:59.24+00:00

    Below is a basic example using the linked docs. It assumes the XML message ends with </root>.

    Client

    using System;
    
    namespace ClientConsole
    {
        using System;
        using System.Net;
        using System.Net.Sockets;
        using System.Threading;
        using System.Text;
    
        // State object for receiving data from remote device.  
        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 AsynchronousClient
        {
            // The port number for the remote device.  
            private const int port = 11000;
    
            // ManualResetEvent instances signal completion.  
            private static ManualResetEvent connectDone =
                new ManualResetEvent(false);
            private static ManualResetEvent sendDone =
                new ManualResetEvent(false);
            private static ManualResetEvent receiveDone =
                new ManualResetEvent(false);
    
            // The response from the remote device.  
            private static String response = String.Empty;
    
            private static void StartClient()
            {
                // Connect to a remote device.  
                try
                {
                    // Establish the remote endpoint for the socket.  
                    // The name of the
                    // remote device is "host.contoso.com".  
                    IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
                    IPAddress ipAddress = ipHostInfo.AddressList[0];
                    IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);
    
                    // Create a TCP/IP socket.  
                    Socket client = new Socket(ipAddress.AddressFamily,
                        SocketType.Stream, ProtocolType.Tcp);
    
                    // Connect to the remote endpoint.  
                    client.BeginConnect(remoteEP,
                        new AsyncCallback(ConnectCallback), client);
                    connectDone.WaitOne();
    
                    // Send test data to the remote device.  
                    string data = "<root><text_req1 /></root>";
                    //data = $"{data.Length}\r{data}";
                    //Console.WriteLine($"Sending: {data}");
                    Send(client, data);
                    sendDone.WaitOne();
    
                    // Receive the response from the remote device.  
                    Receive(client);
                    receiveDone.WaitOne();
    
                    // Write the response to the console.  
                    Console.WriteLine("Response received : {0}", response);
    
                    // Release the socket.  
    
                    //client.Shutdown(SocketShutdown.Both);
                    //client.Close();
    
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.ToString());
                }
            }
    
            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 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 > 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 > 1)
                        {
                            response = state.sb.ToString();
                        }
                        // Signal that all bytes have been received.  
                        receiveDone.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, 0,
                    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());
                }
            }
    
            public static int Main(String[] args)
            {
                bool active = true;
                while (active)
                {
                    StartClient();
    
                    Console.Write("Press enter to continue.  Enter S to stop.");
                    var input = Console.ReadLine();
                    if(input.ToUpper() == "S" )
                    {
                        active = false;
    
                    }
                }
    
                return 0;
            }
        }
    }
    

    Server

    using System;
    
    namespace ServerConsole
    {
        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
        {
            // 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();
    
            // Client socket.
            public Socket workSocket = null;
        }
    
        public class AsynchronousSocketListener
        {
            // Thread signal.  
            public static ManualResetEvent allDone = new ManualResetEvent(false);
    
            public AsynchronousSocketListener()
            {
            }
    
            public static void StartListening()
            {
                // Establish the local endpoint for the socket.  
                // The DNS name of the computer  
                // running the listener is "host.contoso.com".  
                IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
    
                Console.WriteLine(ipHostInfo.HostName);
    
                IPAddress ipAddress = ipHostInfo.AddressList[0];
                IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
    
                // Create a TCP/IP socket.  
                Socket listener = new Socket(ipAddress.AddressFamily,
                    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 > 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("</root>") > -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;
            }
        }
    }
    
    1 person found this answer helpful.

  2. AgaveJoe 26,191 Reputation points
    2021-06-20T17:18:38.913+00:00

    Can you help me, show how to get your code into a WPF application?

    Copy and paste.

    namespace SocketServer
    {
        /// <summary>
        /// Interaction logic for MainWindow.xaml
        /// </summary>
        public partial class MainWindow : Window
        {
            public MainWindow()
            {
                InitializeComponent();
                AsynchronousSocketListener.StartListening();
            }
        }
    
    
        public class StateObject
        {
            // 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();
    
            // Client socket.
            public Socket workSocket = null;
        }
    
        public class AsynchronousSocketListener
        {
            // Thread signal.  
            public static ManualResetEvent allDone = new ManualResetEvent(false);
    
            public AsynchronousSocketListener()
            {
            }
    
            public static void StartListening()
            {
                // Establish the local endpoint for the socket.  
                // The DNS name of the computer  
                // running the listener is "host.contoso.com".  
                IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
    
                Console.WriteLine(ipHostInfo.HostName);
    
                IPAddress ipAddress = ipHostInfo.AddressList[0];
                IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
    
                // Create a TCP/IP socket.  
                Socket listener = new Socket(ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
    
                listener.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, 0);
    
                // 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 > 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("</root>") > -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;
            //}
        }
    }