c#中的Winsock服务器/客户端应用程序

Question

I'm working to make a Client/Server Application in C# using winsock Control. I done every thing in that but i stuck the place of sending data from client to server. In my program server always listen the client using the ip and port. I send the data from the client to server.

1)When click the Listen button on the server form it open the server where client is connect.

2)In Client form 1st i click the connect button for that the server is connected Gives an message (Connect Event: ip) for this message we easly know that the client is connected to the server.

3)Then we enter some data in the Send Data text Box then click Send Button to send the data to server and also save in client.

Code Below:

SERVER:

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Net;
using System.Threading;
using System.Net.Sockets;

namespace Server
{
    public partial class Form1 : Form
    {      
        public Form1()
        {
            InitializeComponent();        
        }
        const string DEFAULT_SERVER = "ip";
        const int DEFAULT_PORT = 120;

        System.Net.Sockets.Socket serverSocket;
        System.Net.Sockets.SocketInformation serverSocketInfo;

        public string Startup()
        {               
            IPHostEntry hostInfo = Dns.GetHostByName(DEFAULT_SERVER);
            IPAddress serverAddr = hostInfo.AddressList[0];
            var serverEndPoint = new IPEndPoint(serverAddr, DEFAULT_PORT);            
            serverSocket = new System.Net.Sockets.Socket(System.Net.Sockets.AddressFamily.InterNetwork, System.Net.Sockets.SocketType.Stream, System.Net.Sockets.ProtocolType.Tcp);
            serverSocket.Bind(serverEndPoint);

            return serverSocket.LocalEndPoint.ToString();    
        }

        public string Listen()
        {
            int backlog = 0;
            try
            {
                serverSocket.Listen(backlog);
                return "Server listening";
            }
            catch (Exception ex)
            {
                return "Failed to listen" + ex.ToString();
            }
        }
        public string ReceiveData()
        {
            System.Net.Sockets.Socket receiveSocket;

            byte[] buffer = new byte[256];

            receiveSocket = serverSocket.Accept();

            var bytesrecd = receiveSocket.Receive(buffer);

            receiveSocket.Close();

            System.Text.Encoding encoding = System.Text.Encoding.UTF8;

            return encoding.GetString(buffer);
        }           

        private void Listen_Click(object sender, EventArgs e)
        {
            string serverInfo = Startup();
            textBox1.Text = "Server started at:" + serverInfo;

            serverInfo = Listen();
            textBox1.Text = serverInfo;

            //string datatosend = Console.ReadLine();
            //SendData(datatosend);

            serverInfo = ReceiveData();
            textBox1.Text = serverInfo;

            //Console.ReadLine();
        }

        private void winsock_DataArrival(object sender, AxMSWinsockLib.DMSWinsockControlEvents_DataArrivalEvent e)
        {
            ReceiveData();
            Listen();
        }

        private void winsock_ConnectEvent(object sender, EventArgs e)
        {
            Listen();
        }
    }
}

This all are work perfectly But here my problem is that i get data form the client to server at only one time. When i send data again from the client to the server its not working and gives me some Message like

Additional information: Only one usage of each socket address (protocol/network address/port) is normally permitted

In the server form

serverSocket.Bind(serverEndPoint);

Please someone help me to solve my problem.

Thank you.

Answer 1

Try this. It helps you

 delegate void AddTextCallback(string text);

        public Form1()
        {
            InitializeComponent();
        }
        private void ButtonConnected_Click(object sender, EventArgs e)
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(ServerHandler));
        }

        private void ServerHandler(object state)
        {
            TcpListener _listner = new TcpListener(IPAddress.Parse("12.2.54.658"), 145);

            _listner.Start();

            AddText("Server started - Listening on port 145");

            Socket _sock = _listner.AcceptSocket();

            //AddText("User from IP " + _sock.RemoteEndPoint);

            while (_sock.Connected)
            {
                byte[] _Buffer = new byte[1024];

                int _DataReceived = _sock.Receive(_Buffer);

                if (_DataReceived == 0)
                {
                    break;
                }

                AddText("Message Received...");

                string _Message = Encoding.ASCII.GetString(_Buffer);

                AddText(_Message);
            }

            _sock.Close();
            AddText("Client Disconnected.");

            _listner.Stop();
            AddText("Server Stop.");
        }

        private void AddText(string text)
        {
            if (this.listBox1.InvokeRequired)
            {
                AddTextCallback d = new AddTextCallback(AddText);
                this.Invoke(d, new object[] { text });
            }
            else
            {
                this.listBox1.Items.Add(text);
            }
        }

I'm also have the same problem like you on last month but i solve that using this http://stackoverflow.com/questions/21072100/receive-multiple-different-messages-tcp-listner-c-sharp from stackoverflow. This helps me lot hope it helps to solve your problem also.

Answer 2

I'm not 100% sure you understand TCP sockets so here goes.

When you use a TCP listener socket you first bind to a port so that clients have a fixed, known point to connect to. This reserves the port for your socket until you give it up by calling Close() on that socket.

Next you Listen in order to begin the process of accepting clients on the port you bound to. You can do both this and the first step in one but as you haven't I haven't here.

Next you call Accept() . This blocks (halts execution) until a client connects and then it returns a socket which is dedicated to communication with that client. If you want to allow another client to connect, you have to call Accept() again.

You can then communicate with your client using the socket that was returned by Accept() until you're done, at which point you call Close() on that socket.

When you're done listening for new connections you call Close() on your listener socket.

---

However when you press your listen button the following happens:

You bind correctly, you begin listening correctly and then your call to ReceiveData() blocks on the Accept call until a client is received. You then receive some data (though this is TCP so that might not be the whole data!) and then you instantly close the connection to your client.

I presume to get the error you're getting you must then press listen again on your server. This therefore restarts the whole listener socket and when you get to bind to the port the second time your previous listener is still bound to it and thus the call fails because something's already allocated on that port.

---

Solution wise you need to keep the socket returned from the Accept() call open until you're done with it. Have the client handle the close by calling the Shutdown() method on their socket or establish some convention for marking the end of communication.

You're also going to run into trouble when you try and have multiple users connected and so at some point you're either going to require threads or some asynchronous sockets but I feel that's out the scope of this question.

Answer 3

我建议你不要使用 AxMSWinsockLib .. 看看这里给出的套接字示例，它显示了如何创建客户端套接字和服务器套接字 - https://msdn.microsoft.com/en-us/library/kb5kfec7(v= vs.110).aspx和这个 - https://msdn.microsoft.com/en-us/library/6y0e13d3(v=vs.110).aspx