以下示例程序实现简单的Socket通信，可以开多个客户端。本机测试通过，未做联机测试。

Server：

using System.Net;

using System.Net.Sockets;

using System.Threading;

using System.Collections;

namespace MySocketServer1

{

    public partial class Form1 : Form

    {

        private IPAddress serverIP = IPAddress.Parse("127.0.0.1");//以本机作测试

        private IPEndPoint serverFullAddr;//完整终端地址

        private Socket sock;

        private System.Timers.Timer myTimer;

        private ArrayList alSock;//当建立了多个连接时用于保存连接

        public Form1()

        {

            InitializeComponent();

        }

        private void btStart_Click(object sender, EventArgs e)

        {

            serverFullAddr = new IPEndPoint(serverIP, 1000);//取端口号1000

//构造Socket对象，套接字类型为“流套接字”，指定五元组中的协议元

            sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream,

ProtocolType.Tcp);

//指定五元组中的本地二元，即本地主机地址和端口号

            sock.Bind(serverFullAddr);

//监听是否有连接传入，指定挂起的连接队列的最大值为20

            sock.Listen(20);

            alSock = new ArrayList();

//构造定时器，时间间隙为1秒，即每隔一秒执行一次accept()方法，以获取连接请求队列中//第一个挂起的连接请求

            myTimer =new System.Timers.Timer(1000);

            myTimer.Elapsed +=new System.Timers.ElapsedEventHandler(myTimer_Elapsed);

            myTimer.Enabled = true;

        }

        private void myTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)

        {

            myTimer.Enabled = false;

//执行accept()，当挂起队列为空时将阻塞本线程，同时由于上一语句，定时器将停止，直//至有连接传入

            Socket acceptSock = sock.Accept();

//将accept()产生的Socket对象存入ArrayList

            alSock.Add(acceptSock);

// 构造Threading.Timer对象，这将导致程序另启线程。线程将执行回调函数，该委托限制//函数参数须为object型。Threading.Timer构造器的第二个参数即传入回调函数的参数；第//三个参数指定调用回调函数之前的延时，取0则立即启动；最后一个参数指定调用回调函数//的时间间隔，取0则只执行一次。

            System.Threading.Timer ti = new System.Threading.Timer(new

TimerCallback(ReceiveMsg), acceptSock, 0, 0);

            myTimer.Enabled = true;

        }

        private void ReceiveMsg(object obj)

        {

            Socket acceptSock = (Socket)obj;

            try

            {

                while (true)

                {

                    byte[] byteArray = new byte[100];

                    acceptSock.Receive(byteArray);//接收数据

//将字节数组转成字符串

                    string strRec = System.Text.Encoding.UTF8.GetString(byteArray);

                    if (this.rtbReceive.InvokeRequired)

                    {

                        this.rtbReceive.Invoke(new EventHandler(this.ChangeRickTextBox), new

object[] { strRec, EventArgs.Empty });

                    }

                }

            }

            catch(Exception ex)

            {

                acceptSock.Close();

                MessageBox.Show("S:Receive Message Error"+ex.Message);

            }

        }

        private void ChangeRickTextBox(object obj,EventArgs e)

        {

            string s = System.Convert.ToString(obj);

            this.rtbReceive.AppendText(s + Environment.NewLine);

        }

        private void btSend_Click(object sender, EventArgs e)

        {

            Socket sc=null;

            byte[] byteSend =

System.Text.Encoding.UTF8.GetBytes(this.tbSend.Text.ToCharArray());

            try

            {

//同时存在若干个客户端连接时，在textBox1中输入要发送的是哪个连接

                int index = int.Parse(this.textBox1.Text.Trim());

                sc = (Socket)alSock[index - 1];

//发送数据

                sc.Send(byteSend);

            }

            catch(Exception ex)

            {

if(sc != null)

{

                sc.Close();

}

                MessageBox.Show("S:Send Message Error"+ex.Message);

            }

        }

        private void btClose_Click(object sender, EventArgs e)

        {

            try

            {

                Application.Exit();

            }

            catch (Exception ex)

            {

                MessageBox.Show("S:Close Socket Error" + ex.Message);

            }

        }

    }

}

== == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == ==

Client:

using System.Net;

using System.Net.Sockets;

using System.Threading;

namespace MySocketClient1

{

    public partial class Form1 : Form

    {

        private IPAddress serverIP = IPAddress.Parse("127.0.0.1");

        private IPEndPoint serverFullAddr;

        private Socket sock;

        public Form1()

        {

            InitializeComponent();

        }

        private void btConnect_Click(object sender, EventArgs e)

        {

            try

            {

                serverFullAddr = new IPEndPoint(serverIP, 1000);

                sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream,

ProtocolType.Tcp);

                sock.Connect(serverFullAddr);//建立与远程主机的连接

//启动新线程用于接收数据

                Thread t = new Thread(new ThreadStart(ReceiveMsg));

                t.Name = "Receive Message";

//一个线程或者是后台线程或者是前台线程。后台线程与前台线程类似，区别是后台线//程不会防止进程终止。一旦属于某一进程的所有前台线程都终止，公共语言运行库就//会通过对任何仍然处于活动状态的后台线程调用 Abort 来结束该进程。

                t.IsBackground = true;

                t.Start();

            }

            catch(Exception ex)

            {

                MessageBox.Show(ex.Message);

            }

        }

        private void ReceiveMsg()

        {

            try

            {

                while (true)

                {

                    byte[] byteRec = new byte[100];

                    this.sock.Receive(byteRec);

                    string strRec = System.Text.Encoding.UTF8.GetString(byteRec);

                    if (this.rtbReceive.InvokeRequired)

                    {

                        this.rtbReceive.Invoke(new EventHandler(ChangeRtb), new object[]

{ strRec, EventArgs.Empty });

                    }

                }

            }

            catch(Exception ex)

            {

                MessageBox.Show("Receive Message Error"+ex.Message);

            }

        }

        private void ChangeRtb(object obj, EventArgs e)

        {

            string s = System.Convert.ToString(obj);

            this.rtbReceive.AppendText(s + Environment.NewLine);

        }

        private void btSend_Click(object sender, EventArgs e)

        {

            byte[] byteSend =

System.Text.Encoding.UTF8.GetBytes(this.tbSend.Text.ToCharArray());

            try

            {

                this.sock.Send(byteSend);

            }

            catch

            {

                MessageBox.Show("Send Message Error");

            }

        }

        private void btClose_Click(object sender, EventArgs e)

        {

            try

            {

                this.sock.Shutdown(SocketShutdown.Receive);

                this.sock.Close();

                Application.Exit();

            }

            catch

            {

                MessageBox.Show("Exit Error");

            }

        }

    }

}

不解之处：

Client端红色标注语句：this.sock.Shutdown(SocketShutdown.Receive)，如改成

this.sock.Shutdown(SocketShutdown.Both);或this.sock.Shutdown(SocketShutdown.Send);

则当点击Cloce按钮时，CPU使用率疯涨到100%，而使用this.sock.Shutdown(SocketShutdown.Receive);

或不调用Shutdown()方法则没有这个问题。难道客户端不应该用Shutdown()？

http://www.cnblogs.com/KissKnife/archive/2006/08/13/475707.html