参看此链接        http://www.cnblogs.com/longwu/archive/2011/08/25/2153636.html

        在上述代码的基础上进行了修改，包括一些捕获异常以及按钮的应用，扩充了一个listbox确保服务端可以选择和不同的客户端进行通信。

服务器代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Net.Sockets;
using System.Net;
using System.Collections;
namespace chat1
{public partial class Form1 : Form{public Form1(){InitializeComponent();StartPosition = FormStartPosition.CenterScreen;//关闭对文本框的非线程操作检查TextBox.CheckForIllegalCrossThreadCalls = false;}string RemoteEndPoint;     //客户端的网络结点Thread threadwatch = null;//负责监听客户端的线程Socket socketwatch = null;//负责监听客户端的套接字//创建一个和客户端通信的套接字Dictionary<string, Socket> dic = new Dictionary<string, Socket> { };   //定义一个集合，存储客户端信息private void button1_Click(object sender, EventArgs e){this.button1.Enabled = false;//定义一个套接字用于监听客户端发来的消息，包含三个参数（IP4寻址协议，流式连接，Tcp协议）socketwatch = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);//服务端发送信息需要一个IP地址和端口号IPAddress address = IPAddress.Parse(textBox1.Text.Trim());//获取文本框输入的IP地址//将IP地址和端口号绑定到网络节点point上IPEndPoint point = new IPEndPoint(address,int.Parse(textBox2.Text.Trim()));//获取文本框上输入的端口号//此端口专门用来监听的//监听绑定的网络节点socketwatch.Bind(point);//将套接字的监听队列长度限制为20socketwatch.Listen(20);            //创建一个监听线程threadwatch = new Thread(watchconnecting);             //将窗体线程设置为与后台同步，随着主线程结束而结束threadwatch.IsBackground = true;   //启动线程   threadwatch.Start();   //启动线程后 textBox3文本框显示相应提示textBox3.AppendText("开始监听客户端传来的信息!" + "\r\n");          }void OnlineList_Disp(string Info){listBoxOnlineList.Items.Add(Info);   //在线列表中显示连接的客户端套接字}//监听客户端发来的请求private void watchconnecting(){Socket connection = null;while (true)  //持续不断监听客户端发来的请求   {try  {   connection = socketwatch.Accept();  }   catch (Exception ex)   {  textBox3.AppendText(ex.Message); //提示套接字监听异常   break;   }//获取客户端的IP和端口号IPAddress clientIP = (connection.RemoteEndPoint as IPEndPoint).Address;int clientPort = (connection.RemoteEndPoint as IPEndPoint).Port;//让客户显示"连接成功的"的信息string sendmsg = "连接服务端成功！\r\n" + "本地IP:" + clientIP + "，本地端口" + clientPort.ToString();byte[] arrSendMsg = Encoding.UTF8.GetBytes(sendmsg); connection.Send(arrSendMsg);RemoteEndPoint = connection.RemoteEndPoint.ToString(); //客户端网络结点号textBox3.AppendText("成功与" + RemoteEndPoint + "客户端建立连接！\t\n");     //显示与客户端连接情况dic.Add(RemoteEndPoint, connection);    //添加客户端信息OnlineList_Disp(RemoteEndPoint);    //显示在线客户端              //IPEndPoint netpoint = new IPEndPoint(clientIP,clientPort);                IPEndPoint netpoint = connection.RemoteEndPoint as IPEndPoint;                //创建一个通信线程    ParameterizedThreadStart pts = new ParameterizedThreadStart(recv);Thread thread = new Thread(pts);   thread.IsBackground = true;//设置为后台线程，随着主线程退出而退出   //启动线程   thread.Start(connection);   }   }///   /// 接收客户端发来的信息    ///   ///客户端套接字对象  private void recv(object socketclientpara){            Socket socketServer = socketclientpara as Socket;while (true)   {   //创建一个内存缓冲区 其大小为1024*1024字节  即1M   byte[] arrServerRecMsg = new byte[1024 * 1024];   //将接收到的信息存入到内存缓冲区,并返回其字节数组的长度  try{int length = socketServer.Receive(arrServerRecMsg);//将机器接受到的字节数组转换为人可以读懂的字符串   string strSRecMsg = Encoding.UTF8.GetString(arrServerRecMsg, 0, length);                    //将发送的字符串信息附加到文本框txtMsg上   textBox3.AppendText("客户端:" + socketServer.RemoteEndPoint+",time:" + GetCurrentTime() + "\r\n" + strSRecMsg + "\r\n\n");}catch (Exception ex){textBox3.AppendText("客户端"+socketServer.RemoteEndPoint+"已经中断连接"+"\r\n"); //提示套接字监听异常 listBoxOnlineList.Items.Remove(socketServer.RemoteEndPoint.ToString());//从listbox中移除断开连接的客户端socketServer.Close();//关闭之前accept出来的和客户端进行通信的套接字break;   }}          }///    /// 获取当前系统时间的方法   ///    /// 当前时间   private DateTime GetCurrentTime()   {   DateTime currentTime = new DateTime();   currentTime = DateTime.Now;   return currentTime;   }//发送信息到客户端 private void button2_Click(object sender, EventArgs e){string sendMsg = textBox4.Text.Trim();  //要发送的信息byte[] bytes = System.Text.Encoding.UTF8.GetBytes(sendMsg);   //将要发送的信息转化为字节数组，因为Socket发送数据时是以字节的形式发送的if (listBoxOnlineList.SelectedIndex == -1){MessageBox.Show("请选择要发送的客户端！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Stop);}else{string selectClient = listBoxOnlineList.Text;  //选择要发送的客户端dic[selectClient].Send(bytes);   //发送数据textBox4.Clear();textBox3.AppendText(label4.Text + GetCurrentTime() + "\r\n" + sendMsg + "\r\n");   }                   }//快捷键 Enter 发送信息 private void textBox4_KeyDown(object sender, KeyEventArgs e){//如果用户按下了Enter键   if (e.KeyCode == Keys.Enter){string sendMsg = textBox4.Text.Trim();  //要发送的信息byte[] bytes = System.Text.Encoding.UTF8.GetBytes(sendMsg); if (listBoxOnlineList.SelectedIndex == -1){MessageBox.Show("请选择要发送的客户端！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Stop);}else{string selectClient = listBoxOnlineList.Text;  //选择要发送的客户端dic[selectClient].Send(bytes);   //发送数据textBox4.Clear();textBox3.AppendText(label4.Text + GetCurrentTime() + "\r\n" + sendMsg + "\r\n");}}}private void Form1_Load(object sender, EventArgs e){}private void Form1_FormClosing(object sender, FormClosingEventArgs e){DialogResult result = MessageBox.Show("是否退出？选否,最小化到托盘", "操作提示", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);if (result == DialogResult.Yes){this.Dispose();}else if (result == DialogResult.Cancel){e.Cancel = true;}else{e.Cancel = true;this.WindowState = FormWindowState.Minimized;this.Visible = false;this.notifyIcon1.Visible = true;this.ShowInTaskbar = false;}}private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e){base.Visible = true;this.notifyIcon1.Visible = false;this.ShowInTaskbar = true;//base.Show();base.WindowState = FormWindowState.Normal;} }
}

 客户端的代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Net.Sockets;
using System.Net;namespace chat2
{public partial class Form1 : Form{public Form1(){InitializeComponent();StartPosition = FormStartPosition.CenterScreen;//关闭对文本框的非法线程操作检查TextBox.CheckForIllegalCrossThreadCalls = false;}//创建 1个客户端套接字 和1个负责监听服务端请求的线程Thread threadclient = null;Socket socketclient = null;List<IPEndPoint> mlist =new List<IPEndPoint>();private void button1_Click(object sender, EventArgs e){//SocketException exception;this.button1.Enabled = false;//定义一个套接字监听socketclient = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);//获取文本框中的IP地址IPAddress address = IPAddress.Parse(textBox1.Text.Trim());//将获取的IP地址和端口号绑定在网络节点上IPEndPoint point = new IPEndPoint(address,int.Parse(textBox2.Text.Trim()));try{//客户端套接字连接到网络节点上，用的是Connectsocketclient.Connect(point);}catch (Exception ){//MessageBox.MessageBox.Show("连接失败\r\n");this.button1.Enabled = true;return;}threadclient=new Thread(recv);threadclient.IsBackground=true;threadclient.Start();}// 接收服务端发来信息的方法  private void recv()//{int x = 0;while (true)//持续监听服务端发来的消息{try{//定义一个1M的内存缓冲区，用于临时性存储接收到的消息byte[] arrRecvmsg = new byte[1024 * 1024];//将客户端套接字接收到的数据存入内存缓冲区，并获取长度int length = socketclient.Receive(arrRecvmsg);//将套接字获取到的字符数组转换为人可以看懂的字符串string strRevMsg = Encoding.UTF8.GetString(arrRecvmsg, 0, length);if (x == 1){textBox3.AppendText("服务器:" + GetCurrentTime() + "\r\n" + strRevMsg + "\r\n\n");}else{textBox3.AppendText(strRevMsg + "\r\n\n");x = 1;}}catch(Exception ex){textBox3.AppendText("远程服务器已经中断连接"+"\r\n");this.button1.Enabled = true;break;}}}//获取当前系统时间private DateTime GetCurrentTime(){DateTime currentTime = new DateTime();currentTime = DateTime.Now;return currentTime; }//发送字符信息到服务端的方法private void ClientSendMsg(string sendMsg){//将输入的内容字符串转换为机器可以识别的字节数组   byte[] arrClientSendMsg = Encoding.UTF8.GetBytes(sendMsg);   //调用客户端套接字发送字节数组   socketclient.Send(arrClientSendMsg);   //将发送的信息追加到聊天内容文本框中   textBox3.AppendText(this.label4.Text+": " + GetCurrentTime() + "\r\n" + sendMsg + "\r\n\n"); }//点击按钮button2 向服务端发送信息 private void button2_Click(object sender, EventArgs e){//调用ClientSendMsg方法 将文本框中输入的信息发送给服务端   ClientSendMsg(textBox4.Text.Trim());textBox4.Clear();}private void textBox4_KeyDown_1(object sender, KeyEventArgs e){//当光标位于文本框时 如果用户按下了键盘上的Enter键if (e.KeyCode == Keys.Enter){//则调用客户端向服务端发送信息的方法  ClientSendMsg(textBox4.Text.Trim());textBox4.Clear();}}private void Form1_Load(object sender, EventArgs e){}private void Form1_FormClosing(object sender, FormClosingEventArgs e){DialogResult result = MessageBox.Show("是否退出？选否,最小化到托盘", "操作提示", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);if (result == DialogResult.Yes){this.Dispose();}else if (result == DialogResult.Cancel){e.Cancel = true;}else{e.Cancel = true;this.WindowState = FormWindowState.Minimized;this.Visible = false;this.notifyIcon1.Visible = true;this.ShowInTaskbar = false;}}private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e){base.Visible = true;this.notifyIcon1.Visible = false;this.ShowInTaskbar = true;//base.Show();base.WindowState = FormWindowState.Normal;}}
}

程序还有不足，后期还会继续改进

客户端在断开连接后，应该把socket关闭；

if (result == DialogResult.Yes)

 {
if (socketclient == null)
{
this.Dispose();
}
else
{
socketclient.Close();
this.Dispose();
}

                      }

其他错误，欢迎大家指出，需要完善的地方，也希望大家给出建议

作者:Chuck Lu GitHub

https://www.cnblogs.com/chucklu/archive/2012/11/23/2784733.html