网络聊天工具Socket编程

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);
            }
        }
    }
}