网络聊天工具Socket编程心得

首先要了解TCP协议通信的流程：
1。服务器端首先创建服务器套接字
2。服务器套接字监听一个端口，等待客户端的请求
3。客户端创建一个客户端套接字
4。客户端向服务器发送请求
5。服务器确认与客户端的连接
6。客户端和服务器利用建立的连接进行通信
7。通信完毕后，客户端和服务器关闭各自的连接


Socket编程基础：
一。利用Socket建立服务器程序
1。创建一个服务器套接字，用IP地址和端口初始化服务器

IPAddress ipAddress  =  IPAddress.Parse( " 127.0.0.1 " );
TcpListener listener  =   new  TcpListener(ipAddress,  1234 );

2。监听服务器端口

listener.Start();

3。确认与客户端的连接

Socket socket  =  listener.AcceptSocket();

4。取得客户端传送过来的信息

// 将传送过来的信息存入字节数组中
byte [] buffer  =   new   byte [ 1024 ];
socket.Receive(buffer);

5。处理客户端的请求并回应客户端

string  message  =   " hello " ;
byte [] outbytes  =  System.Text.Encoding.ASCII.GetBytes(message.ToCharArray());
socket.Send(outbytes, message.Length,  0 );

6。断开客户端的连接，释放客户端连接

socket.Close();

7。关闭服务器，释放服务器连接

listener.Close();

二。利用Socket建立客户端程序
1。创建客户端套接字

TcpClient tcpClient  =   new  TcpClient();

2。连接服务器

tcpClient.Connect(IPAddress.Parse( " 127.0.0.1 " ),  1234 );

3。得到与服务器通信的流通道

NetworkStream stream  =  tcpClient.GetStream();

4。向服务器发送数据

string  cmd  =   " " ;
byte [] outbytes  =  System.Text.Encoding.ASCII.GetBytes(cmd.ToCharArray());
stream.Write(outbytes,  0 , outbytes.Length);

5。接收从服务器发回的数据

byte [] buffer  =   new   byte [ 1024 ];
int  len  =  stream.Read(buffer,  0 , buffer.Length);
string  msg  =  System.Text.Encoding.ASCII.GetString(buffer,  0 , len);

6。断开连接

tcpClient.Close();

 

服务器端窗体ChatServer.cs:

using  System;
using  System.Drawing;
using  System.Collections;
using  System.ComponentModel;
using  System.Windows.Forms;
using  System.Data;
using  System.Net;
using  System.Net.Sockets;
using  System.Threading;

namespace  ChatServer
{
     ///   <summary>
     ///  Form1 的摘要说明。
     ///   </summary>
     public   class  ChatServerForm : System.Windows.Forms.Form
    {
         ///   <summary>
         ///  必需的设计器变量。
         ///   </summary>
         private  System.ComponentModel.Container components  =   null ;
         //  The port
         static   int  port  =   1234 ;
         private  TcpListener listener;
         private  Socket tmpSocket;
         //  The maximal clients the server can hold
         static   int  MaxNum  =   100 ;
         private  System.Windows.Forms.Label label1;
         private  System.Windows.Forms.Label label2;
         private  System.Windows.Forms.TextBox txtHost;
         private  System.Windows.Forms.TextBox txtPort;
         private  System.Windows.Forms.Button btnStart;
         private  System.Windows.Forms.Button btnExit;
         private  System.Windows.Forms.Label label3;
         private  System.Windows.Forms.ComboBox cmbCurUserList;
         private  System.Windows.Forms.ListBox lstInfo;
         //  The array clients is to save the online clients
         static  ArrayList clients  =   new  ArrayList();

         public  ChatServerForm()
        {
             //
             //  Windows 窗体设计器支持所必需的
             //
            InitializeComponent();

             //
             //  TODO: 在 InitializeComponent 调用后添加任何构造函数代码
             //
        }

         ///   <summary>
         ///  清理所有正在使用的资源。
         ///   </summary>
         protected   override   void  Dispose(  bool  disposing )
        {
             if ( disposing )
            {
                 if  (components  !=   null ) 
                {
                    components.Dispose();
                }
            }
             base .Dispose( disposing );
        }

         #region  Windows 窗体设计器生成的代码
         ///   <summary>
         ///  设计器支持所需的方法 - 不要使用代码编辑器修改
         ///  此方法的内容。
         ///   </summary>
         private   void  InitializeComponent()
        {
             this .label1  =   new  System.Windows.Forms.Label();
             this .label2  =   new  System.Windows.Forms.Label();
             this .txtHost  =   new  System.Windows.Forms.TextBox();
             this .txtPort  =   new  System.Windows.Forms.TextBox();
             this .btnStart  =   new  System.Windows.Forms.Button();
             this .btnExit  =   new  System.Windows.Forms.Button();
             this .label3  =   new  System.Windows.Forms.Label();
             this .cmbCurUserList  =   new  System.Windows.Forms.ComboBox();
             this .lstInfo  =   new  System.Windows.Forms.ListBox();
             this .SuspendLayout();
             //  
             //  label1
             //  
             this .label1.AutoSize  =   true ;
             this .label1.Location  =   new  System.Drawing.Point( 32 ,  32 );
             this .label1.Name  =   " label1 " ;
             this .label1.Size  =   new  System.Drawing.Size( 54 ,  17 );
             this .label1.TabIndex  =   0 ;
             this .label1.Text  =   " 主机号： " ;
             //  
             //  label2
             //  
             this .label2.AutoSize  =   true ;
             this .label2.Location  =   new  System.Drawing.Point( 32 ,  72 );
             this .label2.Name  =   " label2 " ;
             this .label2.Size  =   new  System.Drawing.Size( 54 ,  17 );
             this .label2.TabIndex  =   1 ;
             this .label2.Text  =   " 端口号： " ;
             //  
             //  txtHost
             //  
             this .txtHost.Location  =   new  System.Drawing.Point( 96 ,  24 );
             this .txtHost.Name  =   " txtHost " ;
             this .txtHost.Size  =   new  System.Drawing.Size( 128 ,  21 );
             this .txtHost.TabIndex  =   2 ;
             this .txtHost.Text  =   "" ;
             //  
             //  txtPort
             //  
             this .txtPort.Location  =   new  System.Drawing.Point( 96 ,  64 );
             this .txtPort.Name  =   " txtPort " ;
             this .txtPort.Size  =   new  System.Drawing.Size( 128 ,  21 );
             this .txtPort.TabIndex  =   3 ;
             this .txtPort.Text  =   "" ;
             //  
             //  btnStart
             //  
             this .btnStart.Location  =   new  System.Drawing.Point( 256 ,  24 );
             this .btnStart.Name  =   " btnStart " ;
             this .btnStart.TabIndex  =   4 ;
             this .btnStart.Text  =   " 启动 " ;
             this .btnStart.Click  +=   new  System.EventHandler( this .btnStart_Click);
             //  
             //  btnExit
             //  
             this .btnExit.Location  =   new  System.Drawing.Point( 256 ,  64 );
             this .btnExit.Name  =   " btnExit " ;
             this .btnExit.TabIndex  =   5 ;
             this .btnExit.Text  =   " 退出 " ;
             this .btnExit.Click  +=   new  System.EventHandler( this .btnExit_Click);
             //  
             //  label3
             //  
             this .label3.AutoSize  =   true ;
             this .label3.Location  =   new  System.Drawing.Point( 24 ,  112 );
             this .label3.Name  =   " label3 " ;
             this .label3.Size  =   new  System.Drawing.Size( 91 ,  17 );
             this .label3.TabIndex  =   6 ;
             this .label3.Text  =   " 当前在线用户： " ;
             //  
             //  cmbCurUserList
             //  
             this .cmbCurUserList.Location  =   new  System.Drawing.Point( 120 ,  112 );
             this .cmbCurUserList.Name  =   " cmbCurUserList " ;
             this .cmbCurUserList.Size  =   new  System.Drawing.Size( 136 ,  20 );
             this .cmbCurUserList.TabIndex  =   7 ;
             //  
             //  lstInfo
             //  
             this .lstInfo.ItemHeight  =   12 ;
             this .lstInfo.Location  =   new  System.Drawing.Point( 0 ,  144 );
             this .lstInfo.Name  =   " lstInfo " ;
             this .lstInfo.Size  =   new  System.Drawing.Size( 344 ,  160 );
             this .lstInfo.TabIndex  =   8 ;
             //  
             //  ChatServerForm
             //  
             this .AutoScaleBaseSize  =   new  System.Drawing.Size( 6 ,  14 );
             this .ClientSize  =   new  System.Drawing.Size( 344 ,  301 );
             this .Controls.Add( this .lstInfo);
             this .Controls.Add( this .cmbCurUserList);
             this .Controls.Add( this .label3);
             this .Controls.Add( this .btnExit);
             this .Controls.Add( this .btnStart);
             this .Controls.Add( this .txtPort);
             this .Controls.Add( this .txtHost);
             this .Controls.Add( this .label2);
             this .Controls.Add( this .label1);
             this .Name  =   " ChatServerForm " ;
             this .Text  =   " Form1 " ;
             this .Load  +=   new  System.EventHandler( this .Form1_Load);
             this .ResumeLayout( false );

        }
         #endregion

         ///   <summary>
         ///  应用程序的主入口点。
         ///   </summary>
        [STAThread]
         static   void  Main() 
        {
            Application.Run( new  ChatServerForm());
        }

         private   void  Form1_Load( object  sender, System.EventArgs e)
        {
             this .txtPort.ReadOnly  =   true ;
             this .txtPort.Text  =  port.ToString();
             this .txtHost.Text  =   " 127.0.0.1 " ;
        }

         private   void  btnStart_Click( object  sender, System.EventArgs e)
        {
             try
            {
                IPAddress ip  =  IPAddress.Parse( this .txtHost.Text);
                listener  =   new  TcpListener(ip, port);     // 创建服务器套字
                listener.Start();     // 开始监听服务器端口
                lstInfo.Items.Add( " 服务器已经启动，正在监听 "   +  txtHost.Text  +   " : "   +  txtPort.Text);

                 // 启动一个新的线程，执行方法StartListen，以便在一个独立的进程中执行确认于客户端连接的操作.
                Thread thread  =   new  Thread( new  ThreadStart( this .StartListen));
                thread.Start();
                btnStart.Enabled  =   false ;
            }
             catch (Exception ex)
            {
                lstInfo.Items.Add(ex.Message);
            }
        }

         private   void  StartListen()
        {
             while ( true )
            {
                 try
                {
                     // 当接受到一个客户端请求时,确认与客户端的连接
                    Socket socket  =  listener.AcceptSocket();

                     // 用tmpSocket保存发出请求的客户端实例
                    tmpSocket  =  socket;

                     if  (clients.Count  >=  MaxNum)
                    {
                        tmpSocket.Close();
                    }
                     else
                    {
                         // 启动一个新的线程,执行方法this.ServiceClient,处理用户相应的要求
                        Thread clientService  =   new  Thread( new  ThreadStart( this .ServiceClient));
                        clientService.Start();
                    }
                }
                 catch (Exception ex)
                {
                    lstInfo.Items.Add(ex.Message);
                }
            }
        }

         private   void  ServiceClient()
        {
             // 定义一个数组,用于接收从客户端发送过来的数据,每次所能接收的数据包的最大长度为1024字节
             byte [] buffer  =   new   byte [ 1024 ];
            Socket clientSocket  =  tmpSocket;
             bool  keepConnect  =   true ;

             // 用循环不断地与客户端进行交互,直到客户端发出Exit命令,将keepConnect设置为false
             // 退出循环,关闭连接,中止当前线程
             while (keepConnect)
            {
                 // 接收数据并存入buffer数组中
                clientSocket.Receive(buffer);
                 // 将字符数组转化为字符串
                 string  clientCommand  =  System.Text.Encoding.ASCII.GetString(buffer);
                 string [] tokens  =  clientCommand.Split( ' | ' );
                 // tokens[0]中保存了命令标识符(CONN或CHAT或PRIV或EXIT)
                 if  (tokens[ 0 ]  ==   " CONN " )     //  CONN|用户名|
                {
                    Client _client  =   new  Client(tokens[ 1 ], clientSocket);
                    clients.Add(_client);
                    lstInfo.Items.Add(tokens[ 1 ]  +   "  has joined " );
                     // 将刚连接的用户名加入到当前在线用户列表中
                     this .cmbCurUserList.Items.Add(tokens[ 1 ]);
                     // 对每一个在线用户发送JOIN和LIST信息命令,以此来更新客户端的在线用户列表
                     for ( int  i = 0 ; i < clients.Count; i ++ )
                    {
                        Client client  =  (Client)clients[i];
                         // 向客户端发送JOIN命令,以此来提示有新的客户进入聊天室
                        SendToClient(client,  " JOIN| "   +  tokens[ 1 ]  +   " | " );
                        Thread.Sleep( 100 );
                         string  msgUsers  =   " LIST| "   +  GetUserList();
                         // 向客户端发送LIST命令,以此来更新客户端的当前在线用户列表
                        SendToClient(client, msgUsers);
                    }
                }
                 if  (tokens[ 0 ]  ==   " CHAT " )     //  CHAT|用户名:内容|
                {
                     // 向所有当前在线用户转发此信息
                     for  ( int  i = 0 ; i < clients.Count; i ++ )
                    {
                        Client client  =  (Client)clients[i];
                         // 将"发送者的用户名:发送内容"转发给用户
                        SendToClient(client, tokens[ 1 ]);
                    }
                }
                 if  (tokens[ 0 ]  ==   " PRIV " )     //  PRIV|发送者用户名|接受者用户名|发送内容
                {
                     string  sender  =  tokens[ 1 ];
                     string  receiver  =  tokens[ 2 ];
                     string  content  =  tokens[ 3 ];

                     string  message  =  sender  +   " send to  "   +  receiver  +   " :  "   +  content;

                     // 仅把信息转发给发送者和接收者
                     for  ( int  i = 0 ; i < clients.Count; i ++ )
                    {
                        Client client  =  (Client)clients[i];
                         if  (client.Name  ==  tokens[ 2 ])
                        {
                             this .SendToClient(client, message);
                        }
                         if  (client.Name  ==  tokens[ 1 ])
                        {
                             this .SendToClient(client, message);
                        }
                    }
                }
                 if  (tokens[ 0 ]  ==   " EXIT " )     //  EXIT|用户名
                {
                     for  ( int  i = 0 ; i < clients.Count; i ++ )
                    {
                        Client client  =  (Client)clients[i];
                         string  message  =  tokens[ 1 ]  +   "  has gone! " ;
                         this .SendToClient(client, message);
                         if  (client.Name  ==  tokens[ 1 ])
                        {
                             // 将该用户从对应的Client对象从clients数组中删除
                            clients.RemoveAt(i);
                             // 将该用户名从当前在线用户列表中删除
                             this .cmbCurUserList.Items.Remove(client.Name);
                             // 向客户端发送QUIT命令，以此来关闭客户端程序
                            message  =   " QUIT| " ;
                             this .SendToClient(client, message);
                        }
                    }
                     for  ( int  i = 0 ;i < clients.Count;i ++ )
                    {
                        Client client  =  (Client)clients[i];
                         string  message  =   " LIST| "   +  GetUserList();
                         this .SendToClient(client, message);
                    }
                     this .lstInfo.Items.Add(tokens[ 1 ]  +   "  has gone! " );
                     // 断开与该用户的连接
                    clientSocket.Close();
                    keepConnect  =   false ;
                }

            }
        }

         // 实现向客户端发送命令请求的功能
         private   void  SendToClient(Client client,  string  msg)
        {
            System.Byte[] message  =  System.Text.Encoding.ASCII.GetBytes(msg.ToCharArray());
            client.ClientSocket.Send(message, message.Length,  0 );
        }

         // 以 username1|username2|username3| 的形式返回当前在线用户名列表
         private   string  GetUserList()
        {
             string  list  =   "" ;
             for  ( int  i = 0 ; i < clients.Count; i ++ )
            {
                Client client  =  (Client)clients[i];
                list  +=  client.Name  +   " | " ;
            }
             return  list;
        }

         private   void  btnExit_Click( object  sender, System.EventArgs e)
        {
             this .Close();
            Application.ExitThread();
            Application.Exit();
        }

         // 定义一个Client类,每个当前在线用户都对应这它的一个实例,它包含了当前在线用户名和该用户
         // 与服务器连接的Socket对象,
         public   class  Client
        {
             string  name;
            Socket clSocket;
            
             public  Client( string  _name, Socket _socket)
            {
                name  =  _name;
                clSocket  =  _socket;
            }

             public   string  Name
            {
                 get
                {
                     return  name;
                }
                 set
                {
                    name  =  value;
                }
            }
             public  Socket ClientSocket
            {
                 get  
                {
                     return  clSocket;
                }
                 set
                {
                    clSocket  =  value;
                }
            }
        }
    }
}

客户端主窗体：ChatClient.cs:

using  System;
using  System.Drawing;
using  System.Collections;
using  System.ComponentModel;
using  System.Windows.Forms;
using  System.Net;
using  System.Net.Sockets;
using  System.Threading;

namespace  ChatClient
{
     ///   <summary>
     ///  ChatClientForm 的摘要说明。
     ///   </summary>
     public   class  ChatClientForm : System.Windows.Forms.Form
    {
         private  System.Windows.Forms.Label label1;
         private  System.Windows.Forms.TextBox txtAlias;
         private  System.Windows.Forms.ListBox lstContent;
         private  System.Windows.Forms.Label label2;
         private  System.Windows.Forms.ListBox lstUsers;
         private  System.Windows.Forms.CheckBox chkPrivate;
         private  System.Windows.Forms.TextBox txtSend;
         private  System.Windows.Forms.Button btnSend;
         private  System.Windows.Forms.Button btnExit;
         ///   <summary>
         ///  必需的设计器变量。
         ///   </summary>
         private  System.ComponentModel.Container components  =   null ;

         private  TcpClient tcpClient;     // 与服务器的连接
         private  NetworkStream stream;     // 与服务器数据交互的流通道
         private   string  userAlias;         // 用户名
         private   bool  isPrivate  =   false ;     // 是否为私聊

        [STAThread]
         static   void  Main() 
        {
            Application.Run( new  ChatClientForm());
        }

         public  ChatClientForm()
        {
             //
             //  Windows 窗体设计器支持所必需的
             //
            InitializeComponent();

             //
             //  TODO: 在 InitializeComponent 调用后添加任何构造函数代码
             //
        }

         ///   <summary>
         ///  清理所有正在使用的资源。
         ///   </summary>
         protected   override   void  Dispose(  bool  disposing )
        {
             if ( disposing )
            {
                 if (components  !=   null )
                {
                    components.Dispose();
                }
            }
             base .Dispose( disposing );
        }

         #region  Windows 窗体设计器生成的代码
         ///   <summary>
         ///  设计器支持所需的方法 - 不要使用代码编辑器修改
         ///  此方法的内容。
         ///   </summary>
         private   void  InitializeComponent()
        {
             this .label1  =   new  System.Windows.Forms.Label();
             this .txtAlias  =   new  System.Windows.Forms.TextBox();
             this .lstContent  =   new  System.Windows.Forms.ListBox();
             this .label2  =   new  System.Windows.Forms.Label();
             this .lstUsers  =   new  System.Windows.Forms.ListBox();
             this .chkPrivate  =   new  System.Windows.Forms.CheckBox();
             this .txtSend  =   new  System.Windows.Forms.TextBox();
             this .btnSend  =   new  System.Windows.Forms.Button();
             this .btnExit  =   new  System.Windows.Forms.Button();
             this .SuspendLayout();
             //  
             //  label1
             //  
             this .label1.AutoSize  =   true ;
             this .label1.Location  =   new  System.Drawing.Point( 104 ,  16 );
             this .label1.Name  =   " label1 " ;
             this .label1.Size  =   new  System.Drawing.Size( 42 ,  17 );
             this .label1.TabIndex  =   0 ;
             this .label1.Text  =   " 昵称： " ;
             //  
             //  txtAlias
             //  
             this .txtAlias.Location  =   new  System.Drawing.Point( 208 ,  8 );
             this .txtAlias.Name  =   " txtAlias " ;
             this .txtAlias.ReadOnly  =   true ;
             this .txtAlias.TabIndex  =   1 ;
             this .txtAlias.Text  =   "" ;
             //  
             //  lstContent
             //  
             this .lstContent.ItemHeight  =   12 ;
             this .lstContent.Location  =   new  System.Drawing.Point( 0 ,  40 );
             this .lstContent.Name  =   " lstContent " ;
             this .lstContent.Size  =   new  System.Drawing.Size( 432 ,  172 );
             this .lstContent.TabIndex  =   2 ;
             //  
             //  label2
             //  
             this .label2.AutoSize  =   true ;
             this .label2.Location  =   new  System.Drawing.Point( 0 ,  224 );
             this .label2.Name  =   " label2 " ;
             this .label2.Size  =   new  System.Drawing.Size( 116 ,  17 );
             this .label2.TabIndex  =   3 ;
             this .label2.Text  =   " 当前在线用户列表： " ;
             //  
             //  lstUsers
             //  
             this .lstUsers.ItemHeight  =   12 ;
             this .lstUsers.Location  =   new  System.Drawing.Point( 0 ,  240 );
             this .lstUsers.Name  =   " lstUsers " ;
             this .lstUsers.Size  =   new  System.Drawing.Size( 120 ,  100 );
             this .lstUsers.TabIndex  =   4 ;
             //  
             //  chkPrivate
             //  
             this .chkPrivate.Location  =   new  System.Drawing.Point( 136 ,  240 );
             this .chkPrivate.Name  =   " chkPrivate " ;
             this .chkPrivate.TabIndex  =   5 ;
             this .chkPrivate.Text  =   " 悄悄话 " ;
             this .chkPrivate.CheckedChanged  +=   new  System.EventHandler( this .chkPrivate_CheckedChanged);
             //  
             //  txtSend
             //  
             this .txtSend.Location  =   new  System.Drawing.Point( 136 ,  272 );
             this .txtSend.Name  =   " txtSend " ;
             this .txtSend.Size  =   new  System.Drawing.Size( 288 ,  21 );
             this .txtSend.TabIndex  =   6 ;
             this .txtSend.Text  =   "" ;
             //  
             //  btnSend
             //  
             this .btnSend.Location  =   new  System.Drawing.Point( 136 ,  312 );
             this .btnSend.Name  =   " btnSend " ;
             this .btnSend.TabIndex  =   7 ;
             this .btnSend.Text  =   " 发送 " ;
             this .btnSend.Click  +=   new  System.EventHandler( this .btnSend_Click);
             //  
             //  btnExit
             //  
             this .btnExit.Location  =   new  System.Drawing.Point( 344 ,  312 );
             this .btnExit.Name  =   " btnExit " ;
             this .btnExit.TabIndex  =   8 ;
             this .btnExit.Text  =   " 离开 " ;
             this .btnExit.Click  +=   new  System.EventHandler( this .btnExit_Click);
             //  
             //  ChatClientForm
             //  
             this .AutoScaleBaseSize  =   new  System.Drawing.Size( 6 ,  14 );
             this .ClientSize  =   new  System.Drawing.Size( 432 ,  349 );
             this .Controls.Add( this .btnExit);
             this .Controls.Add( this .btnSend);
             this .Controls.Add( this .txtSend);
             this .Controls.Add( this .chkPrivate);
             this .Controls.Add( this .lstUsers);
             this .Controls.Add( this .label2);
             this .Controls.Add( this .lstContent);
             this .Controls.Add( this .txtAlias);
             this .Controls.Add( this .label1);
             this .Name  =   " ChatClientForm " ;
             this .Text  =   " ChatClientForm " ;
             this .Load  +=   new  System.EventHandler( this .ChatClientForm_Load);
             this .ResumeLayout( false );

        }
         #endregion

         private   void  ChatClientForm_Load( object  sender, System.EventArgs e)
        {
             try
            {
                Login dlgLogin  =   new  Login();
                DialogResult result  =  dlgLogin.ShowDialog();
                 if  (result  ==  DialogResult.OK)
                {
                     this .userAlias  =  dlgLogin.Alias;
                     this .txtAlias.Text  =  userAlias;

                     this .tcpClient  =  dlgLogin.tcpClient;
                    stream  =  tcpClient.GetStream();
                    dlgLogin.Close();
                }
                 else
                {
                    lstUsers.Enabled  =   false ;
                    txtSend.ReadOnly  =   true ;
                    btnSend.Enabled  =   false ;
                    dlgLogin.Close();
                }

                 // 启动一个新的进程，执行方法this.ServerResponse,以便来响应从服务器发回的信息
                Thread thread  =   new  Thread( new  ThreadStart( this .ServerResponse));
                thread.Start();

                 string  cmd  =   " CONN| "   +   this .userAlias  +   " | " ;
                 byte [] outbytes  =  System.Text.Encoding.ASCII.GetBytes(cmd.ToCharArray());

                 // 利用NetworkStream的Write方法传送
                stream.Write(outbytes,  0 , outbytes.Length);
            }
             catch  (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

         private   void  ServerResponse()
        {
             byte [] buffer  =   new   byte [ 1024 ];
             string  msg;
             int  len;
             try
            {
                 if  ( ! stream.CanRead)
                {
                     return ;
                }

                 while  ( true )
                {
                    len  =  stream.Read(buffer,  0 , buffer.Length);
                    msg  =  System.Text.Encoding.ASCII.GetString(buffer,  0 , len);
                    msg.Trim();
                     string [] tokens  =  msg.Split( ' | ' );

                     if  (tokens[ 0 ]  ==   " LIST " )     // LIST|用户名1|用户名2|
                    {
                        lstUsers.Items.Clear();
                         for  ( int  i = 0 ; i < tokens.Length - 1 ; i ++ )
                        {
                            lstUsers.Items.Add(tokens[i].Trim());
                        }
                    }

                     if  (tokens[ 0 ]  ==   " JOIN " )     //  JOIN|刚刚登录的用户名
                    {
                         this .lstContent.Items.Add(tokens[ 1 ]  +   "  has enter the chatroom! " );
                    }

                     if  (tokens[ 0 ]  ==   " QUIT " )
                    {
                         break ;
                    }

                     if  (tokens[ 0 ] != " LIST "   &&  tokens[ 0 ] != " JOIN "   &&  tokens[ 0 ] != " QUIT " )
                    {
                        lstContent.Items.Add(msg);
                    }
                }
                tcpClient.Close();     // 关闭连接
                 this .Close();         // 关闭客户端程序
            }
             catch  (Exception ex)
            {
                lstContent.Items.Add(ex.Message);
            }
        }

         private   void  chkPrivate_CheckedChanged( object  sender, System.EventArgs e)
        {
             if  ( this .chkPrivate.Checked)
            {
                 this .isPrivate  =   true ;
            }
             else
            {
                 this .isPrivate  =   false ;
            }
        }

         private   void  btnSend_Click( object  sender, System.EventArgs e)
        {
             try
            {
                 if  ( ! this .isPrivate)
                {
                     string  message  =   " CHAT| "   +   this .userAlias  +   " : "   +   this .txtSend.Text  +   " | " ;
                     this .txtSend.Text  =   "" ;
                     this .txtSend.Focus();
                     byte [] outbytes  =  System.Text.Encoding.ASCII.GetBytes(message.ToCharArray());
                    stream.Write(outbytes,  0 , outbytes.Length);
                }
                 else
                {
                     if  (lstUsers.SelectedIndex  ==   - 1 )
                    {
                        MessageBox.Show( " 请在列表中选择一个用户 " ,  " 提示信息 " , MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                         return ;
                    }
                     string  receiver  =   this .lstUsers.SelectedItem.ToString();
                     string  message  =   " PRIV| "   +   this .userAlias  +   " | "   +  receiver  +   " | "   +   this .txtSend.Text  +   " | " ;
                     this .txtSend.Text  =   "" ;
                     this .txtSend.Focus();
                     byte [] outbytes  =  System.Text.Encoding.ASCII.GetBytes(message.ToCharArray());
                    stream.Write(outbytes,  0 , outbytes.Length);
                }
            }
             catch  (Exception ex)
            {
                 this .lstContent.Items.Add( " 网络发生错误！ " );
            }
        }

         private   void  btnExit_Click( object  sender, System.EventArgs e)
        {
             string  message  =   " EXIT| "   +   this .userAlias  +   " | " ;
             byte [] outbytes  =  System.Text.Encoding.ASCII.GetBytes(message.ToCharArray());
            stream.Write(outbytes,  0 , outbytes.Length);
        }

    }
}

客户端登录窗体：Login.cs

using  System;
using  System.Drawing;
using  System.Collections;
using  System.ComponentModel;
using  System.Windows.Forms;
using  System.Data;
using  System.Net;
using  System.Net.Sockets;

namespace  ChatClient
{
     ///   <summary>
     ///  Login 的摘要说明。
     ///   </summary>
     public   class  Login : System.Windows.Forms.Form
    {
         ///   <summary>
         ///  必需的设计器变量。
         ///   </summary>
         private  System.ComponentModel.Container components  =   null ;
        
         // tcpClient是Login的一个公有成员，它用于创建客户端套接字
         public  TcpClient tcpClient;
         private  System.Windows.Forms.Label label1;
         private  System.Windows.Forms.Label label2;
         private  System.Windows.Forms.Label label3;
         private  System.Windows.Forms.Button btnLogin;
         private  System.Windows.Forms.Button btnCancel;
         private  System.Windows.Forms.TextBox txtHost;
         private  System.Windows.Forms.TextBox txtPort;
         private  System.Windows.Forms.TextBox txtName;

         // Alias是Login的一个公有成员，它向ChatClient窗体传递用户名
         public   string  Alias  =   "" ;

         public  Login()
        {
             //
             //  Windows 窗体设计器支持所必需的
             //
            InitializeComponent();

             //
             //  TODO: 在 InitializeComponent 调用后添加任何构造函数代码
             //
        }

         ///   <summary>
         ///  清理所有正在使用的资源。
         ///   </summary>
         protected   override   void  Dispose(  bool  disposing )
        {
             if ( disposing )
            {
                 if  (components  !=   null ) 
                {
                    components.Dispose();
                }
            }
             base .Dispose( disposing );
        }

         #region  Windows 窗体设计器生成的代码
         ///   <summary>
         ///  设计器支持所需的方法 - 不要使用代码编辑器修改
         ///  此方法的内容。
         ///   </summary>
         private   void  InitializeComponent()
        {
             this .label1  =   new  System.Windows.Forms.Label();
             this .label2  =   new  System.Windows.Forms.Label();
             this .label3  =   new  System.Windows.Forms.Label();
             this .txtHost  =   new  System.Windows.Forms.TextBox();
             this .txtPort  =   new  System.Windows.Forms.TextBox();
             this .txtName  =   new  System.Windows.Forms.TextBox();
             this .btnLogin  =   new  System.Windows.Forms.Button();
             this .btnCancel  =   new  System.Windows.Forms.Button();
             this .SuspendLayout();
             //  
             //  label1
             //  
             this .label1.AutoSize  =   true ;
             this .label1.Location  =   new  System.Drawing.Point( 16 ,  32 );
             this .label1.Name  =   " label1 " ;
             this .label1.Size  =   new  System.Drawing.Size( 79 ,  17 );
             this .label1.TabIndex  =   0 ;
             this .label1.Text  =   " 服务器地址： " ;
             //  
             //  label2
             //  
             this .label2.AutoSize  =   true ;
             this .label2.Location  =   new  System.Drawing.Point( 16 ,  72 );
             this .label2.Name  =   " label2 " ;
             this .label2.Size  =   new  System.Drawing.Size( 54 ,  17 );
             this .label2.TabIndex  =   1 ;
             this .label2.Text  =   " 端口号： " ;
             //  
             //  label3
             //  
             this .label3.AutoSize  =   true ;
             this .label3.Location  =   new  System.Drawing.Point( 16 ,  112 );
             this .label3.Name  =   " label3 " ;
             this .label3.Size  =   new  System.Drawing.Size( 54 ,  17 );
             this .label3.TabIndex  =   2 ;
             this .label3.Text  =   " 用户名： " ;
             //  
             //  txtHost
             //  
             this .txtHost.Location  =   new  System.Drawing.Point( 104 ,  24 );
             this .txtHost.Name  =   " txtHost " ;
             this .txtHost.Size  =   new  System.Drawing.Size( 144 ,  21 );
             this .txtHost.TabIndex  =   3 ;
             this .txtHost.Text  =   " 127.0.0.1 " ;
             //  
             //  txtPort
             //  
             this .txtPort.Location  =   new  System.Drawing.Point( 104 ,  64 );
             this .txtPort.Name  =   " txtPort " ;
             this .txtPort.ReadOnly  =   true ;
             this .txtPort.Size  =   new  System.Drawing.Size( 144 ,  21 );
             this .txtPort.TabIndex  =   4 ;
             this .txtPort.Text  =   " 1234 " ;
             //  
             //  txtName
             //  
             this .txtName.Location  =   new  System.Drawing.Point( 104 ,  104 );
             this .txtName.Name  =   " txtName " ;
             this .txtName.Size  =   new  System.Drawing.Size( 144 ,  21 );
             this .txtName.TabIndex  =   5 ;
             this .txtName.Text  =   "" ;
             //  
             //  btnLogin
             //  
             this .btnLogin.DialogResult  =  System.Windows.Forms.DialogResult.OK;
             this .btnLogin.Location  =   new  System.Drawing.Point( 40 ,  160 );
             this .btnLogin.Name  =   " btnLogin " ;
             this .btnLogin.TabIndex  =   6 ;
             this .btnLogin.Text  =   " 登录 " ;
             this .btnLogin.Click  +=   new  System.EventHandler( this .btnLogin_Click);
             //  
             //  btnCancel
             //  
             this .btnCancel.DialogResult  =  System.Windows.Forms.DialogResult.Cancel;
             this .btnCancel.Location  =   new  System.Drawing.Point( 168 ,  160 );
             this .btnCancel.Name  =   " btnCancel " ;
             this .btnCancel.TabIndex  =   7 ;
             this .btnCancel.Text  =   " 取消 " ;
             this .btnCancel.Click  +=   new  System.EventHandler( this .btnCancel_Click);
             //  
             //  Login
             //  
             this .AutoScaleBaseSize  =   new  System.Drawing.Size( 6 ,  14 );
             this .ClientSize  =   new  System.Drawing.Size( 292 ,  229 );
             this .Controls.Add( this .btnCancel);
             this .Controls.Add( this .btnLogin);
             this .Controls.Add( this .txtName);
             this .Controls.Add( this .txtPort);
             this .Controls.Add( this .txtHost);
             this .Controls.Add( this .label3);
             this .Controls.Add( this .label2);
             this .Controls.Add( this .label1);
             this .Name  =   " Login " ;
             this .Text  =   " Login " ;
             this .Load  +=   new  System.EventHandler( this .Login_Load);
             this .ResumeLayout( false );

        }
         #endregion


         private   void  Login_Load( object  sender, System.EventArgs e)
        {
        
        }

         private   void  btnCancel_Click( object  sender, System.EventArgs e)
        {
            ChatClient.Login.ActiveForm.Close();
        }

         private   void  btnLogin_Click( object  sender, System.EventArgs e)
        {
             this .txtName.Text  =   this .txtName.Text.Trim();
             if  ( this .txtName.Text.Length  ==   0 )
            {
                MessageBox.Show( " 请输入您的昵称！ " ,  " 提示信息 " , MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                 this .txtName.Focus();
                 return ;
            }
             try
            {
                tcpClient  =   new  TcpClient();
                
                 // 向指定的IP地址的服务器发出连接请求
                tcpClient.Connect(IPAddress.Parse(txtHost.Text), Int32.Parse(txtPort.Text));
                 this .Alias  =  txtName.Text;
            }
             catch  (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}