SOCKET原理（转载）

SOCKET原理

一、套接字（socket）概念

　　套接字（socket）是通信的基石，是支持TCP/IP协议的网络通信的基本操作单元。它是网络通信过程中端点的抽象表示，包含进行网络通信必须的五种信息：连接使用的协议，本地主机的IP地址，本地进程的协议端口，远地主机的IP地址，远地进程的协议端口。

　　应用层通过传输层进行数据通信时，TCP会遇到同时为多个应用程序进程提供并发服务的问题。多个TCP连接或多个应用程序进程可能需要通过同一个 TCP协议端口传输数据。为了区别不同的应用程序进程和连接，许多计算机操作系统为应用程序与TCP／IP协议交互提供了套接字(Socket)接口。应用层可以和传输层通过Socket接口，区分来自不同应用程序进程或网络连接的通信，实现数据传输的并发服务。

二、建立socket连接

　　建立Socket连接至少需要一对套接字，其中一个运行于客户端，称为ClientSocket ，另一个运行于服务器端，称为ServerSocket 。

　　套接字之间的连接过程分为三个步骤：服务器监听，客户端请求，连接确认。

服务器监听：服务器端套接字并不定位具体的客户端套接字，而是处于等待连接的状态，实时监控网络状态，等待客户端的连接请求
客户端请求：指客户端的套接字提出连接请求，要连接的目标是服务器端的套接字。为此，客户端的套接字必须首先描述它要连接的服务器的套接字，指出服务器端套接字的地址和端口号，然后就向服务器端套接字提出连接请求。
连接确认：当服务器端套接字监听到或者说接收到客户端套接字的连接请求时，就响应客户端套接字的请求，建立一个新的线程，把服务器端套接字的描述发给客户端，一旦客户端确认了此描述，双方就正式建立连接。而服务器端套接字继续处于监听状态，继续接收其他客户端套接字的连接请求。

三、SOCKET连接与TCP连接

　　创建Socket连接时，可以指定使用的传输层协议，Socket可以支持不同的传输层协议（TCP或UDP），当使用TCP协议进行连接时，该Socket连接就是一个TCP连接。

四、Socket连接与HTTP连接

　　由于通常情况下Socket连接就是TCP连接，因此Socket连接一旦建立，通信双方即可开始相互发送数据内容，直到双方连接断开。但在实际网络应用中，客户端到服务器之间的通信往往需要穿越多个中间节点，例如路由器、网关、防火墙等，大部分防火墙默认会关闭长时间处于非活跃状态的连接而导致 Socket 连接断连，因此需要通过轮询告诉网络，该连接处于活跃状态。

　　而HTTP连接使用的是“请求—响应”的方式，不仅在请求时需要先建立连接，而且需要客户端向服务器发出请求后，服务器端才能回复数据。

　　很多情况下，需要服务器端主动向客户端推送数据，保持客户端与服务器数据的实时与同步。此时若双方建立的是Socket连接，服务器就可以直接将数据传送给客户端；若双方建立的是HTTP连接，则服务器需要等到客户端发送一次请求后才能将数据传回给客户端，因此，客户端定时向服务器端发送连接请求，不仅可以保持在线，同时也是在“询问”服务器是否有新的数据，如果有就将数据传给客户端。

五、Socket服务端与客户端通信示意图

六、服务端与客户端代码

　　1、服务端

　　（1）服务端窗口设计

 namespace SocketForm

 {

     partial class Form1

     {

         /// <summary>

         /// 必需的设计器变量。

         /// </summary>

         private System.ComponentModel.IContainer components = null;

         /// <summary>

         /// 清理所有正在使用的资源。

         /// </summary>

         /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>

         protected override void Dispose(bool disposing)

         {

             if (disposing && (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.panel1 = new System.Windows.Forms.Panel();

             this.tb_ip = new System.Windows.Forms.TextBox();

             this.lb_Ip = new System.Windows.Forms.Label();

             this.lb_port = new System.Windows.Forms.Label();

             this.tb_port = new System.Windows.Forms.TextBox();

             this.bt_connnect = new System.Windows.Forms.Button();

             this.listBox1 = new System.Windows.Forms.ListBox();

             this.txt_msg = new System.Windows.Forms.TextBox();

             this.bt_send = new System.Windows.Forms.Button();

             this.panel1.SuspendLayout();

             this.SuspendLayout();

             //

             // panel1

             //

             this.panel1.Controls.Add(this.bt_connnect);

             this.panel1.Controls.Add(this.lb_port);

             this.panel1.Controls.Add(this.tb_port);

             this.panel1.Controls.Add(this.lb_Ip);

             this.panel1.Controls.Add(this.tb_ip);

             this.panel1.Location = new System.Drawing.Point(, );

             this.panel1.Name = "panel1";

             this.panel1.Size = new System.Drawing.Size(, );

             this.panel1.TabIndex = ;

             //

             // tb_ip

             //

             this.tb_ip.Location = new System.Drawing.Point(, );

             this.tb_ip.Name = "tb_ip";

             this.tb_ip.Size = new System.Drawing.Size(, );

             this.tb_ip.TabIndex = ;

             this.tb_ip.Text = "127.0.0.1";

             //

             // lb_Ip

             //

             this.lb_Ip.AutoSize = true;

             this.lb_Ip.Location = new System.Drawing.Point(, );

             this.lb_Ip.Name = "lb_Ip";

             this.lb_Ip.Size = new System.Drawing.Size(, );

             this.lb_Ip.TabIndex = ;

             this.lb_Ip.Text = "IP:";

             //

             // lb_port

             //

             this.lb_port.AutoSize = true;

             this.lb_port.Location = new System.Drawing.Point(, );

             this.lb_port.Name = "lb_port";

             this.lb_port.Size = new System.Drawing.Size(, );

             this.lb_port.TabIndex = ;

             this.lb_port.Text = "Port:";

             //

             // tb_port

             //

             this.tb_port.Location = new System.Drawing.Point(, );

             this.tb_port.Name = "tb_port";

             this.tb_port.Size = new System.Drawing.Size(, );

             this.tb_port.TabIndex = ;

             this.tb_port.Text = "";

             //

             // bt_connnect

             //

             this.bt_connnect.Location = new System.Drawing.Point(, );

             this.bt_connnect.Name = "bt_connnect";

             this.bt_connnect.Size = new System.Drawing.Size(, );

             this.bt_connnect.TabIndex = ;

             this.bt_connnect.Text = "开始监听";

             this.bt_connnect.UseVisualStyleBackColor = true;

             this.bt_connnect.Click += new System.EventHandler(this.bt_connnect_Click);

             //

             // listBox1

             //

             this.listBox1.FormattingEnabled = true;

             this.listBox1.ItemHeight = ;

             this.listBox1.Location = new System.Drawing.Point(, );

             this.listBox1.Name = "listBox1";

             this.listBox1.Size = new System.Drawing.Size(, );

             this.listBox1.TabIndex = ;

             //

             // txt_msg

             //

             this.txt_msg.Location = new System.Drawing.Point(, );

             this.txt_msg.Multiline = true;

             this.txt_msg.Name = "txt_msg";

             this.txt_msg.Size = new System.Drawing.Size(, );

             this.txt_msg.TabIndex = ;

             //

             // bt_send

             //

             this.bt_send.Location = new System.Drawing.Point(, );

             this.bt_send.Name = "bt_send";

             this.bt_send.Size = new System.Drawing.Size(, );

             this.bt_send.TabIndex = ;

             this.bt_send.Text = "发送";

             this.bt_send.UseVisualStyleBackColor = true;

             this.bt_send.Click += new System.EventHandler(this.bt_send_Click);

             //

             // Form1

             //

             this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);

             this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;

             this.ClientSize = new System.Drawing.Size(, );

             this.Controls.Add(this.bt_send);

             this.Controls.Add(this.txt_msg);

             this.Controls.Add(this.listBox1);

             this.Controls.Add(this.panel1);

             this.Name = "Form1";

             this.Text = "SocketForm";

             this.Load += new System.EventHandler(this.Form1_Load);

             this.panel1.ResumeLayout(false);

             this.panel1.PerformLayout();

             this.ResumeLayout(false);

             this.PerformLayout();

         }

         #endregion

         private System.Windows.Forms.Panel panel1;

         private System.Windows.Forms.Button bt_connnect;

         private System.Windows.Forms.Label lb_port;

         private System.Windows.Forms.TextBox tb_port;

         private System.Windows.Forms.Label lb_Ip;

         private System.Windows.Forms.TextBox tb_ip;

         private System.Windows.Forms.ListBox listBox1;

         private System.Windows.Forms.TextBox txt_msg;

         private System.Windows.Forms.Button bt_send;

     }

 }

　　（2）服务端逻辑设计

 using System;

 using System.Collections.Generic;

 using System.ComponentModel;

 using System.Data;

 using System.Drawing;

 using System.Linq;

 using System.Net;

 using System.Net.Sockets;

 using System.Text;

 using System.Threading;

 using System.Windows.Forms;

 namespace SocketForm

 {

     public partial class Form1 : Form

     {

         public Form1()

         {

             InitializeComponent();

         }

         private void bt_connnect_Click(object sender, EventArgs e)

         {

             try

             {

                 //点击开始监听时 在服务端创建一个负责监听IP和端口号的Socket

                 Socket socketWatch = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

                 IPAddress ip = IPAddress.Any;

                 //创建对象端口

                 IPEndPoint point = new IPEndPoint(ip, Convert.ToInt32(tb_port.Text));

                 socketWatch.Bind(point);//绑定端口号

                 ShowMsg("监听成功!");

                 socketWatch.Listen();//设置监听

                 //创建监听线程

                 Thread thread = new Thread(Listen);

                 thread.IsBackground = true;

                 thread.Start(socketWatch);

             }

             catch { }

         }

         /// <summary>

         /// 等待客户端的连接 并且创建与之通信的Socket

         /// </summary>

         Socket socketSend;

         void Listen(object o)

         {

             try

             {

                 Socket socketWatch = o as Socket;

                 while (true)

                 {

                     socketSend = socketWatch.Accept();//等待接收客户端连接

                     ShowMsg(socketSend.RemoteEndPoint.ToString() + ":" + "连接成功!");

                     //开启一个新线程，执行接收消息方法

                     Thread r_thread = new Thread(Received);

                     r_thread.IsBackground = true;

                     r_thread.Start(socketSend);

                 }

             }

             catch { }

         }

         /// <summary>

         /// 服务器端不停的接收客户端发来的消息

         /// </summary>

         /// <param name="o"></param>

         void Received(object o)

         {

             try

             {

                 Socket socketSend = o as Socket;

                 while (true)

                 {

                     //客户端连接服务器成功后，服务器接收客户端发送的消息

                     byte[] buffer = new byte[ *  * ];

                     //实际接收到的有效字节数

                     int len = socketSend.Receive(buffer);

                     if (len == )

                     {

                         break;

                     }

                     string str = Encoding.UTF8.GetString(buffer, , len);

                     ShowMsg(socketSend.RemoteEndPoint + ":" + str);

                 }

             }

             catch { }

         }

         /// <summary>

         /// 服务器向客户端发送消息

         /// </summary>

         /// <param name="str"></param>

         void Send(string str) {

             byte[] buffer = Encoding.UTF8.GetBytes(str);

             socketSend.Send(buffer);

         }

         void ShowMsg(string msg)

         {

             listBox1.Items.Add(msg + "\r\n");

         }

         private void Form1_Load(object sender, EventArgs e)

         {

             Control.CheckForIllegalCrossThreadCalls = false;

         }

         private void bt_send_Click(object sender, EventArgs e)

         {

             Send(txt_msg.Text.Trim());

         }

     }

 }

　　2、客户端

　　（1）客户端窗口设计

 namespace SocketClient

 {

     partial class Form1

     {

         /// <summary>

         /// 必需的设计器变量。

         /// </summary>

         private System.ComponentModel.IContainer components = null;

         /// <summary>

         /// 清理所有正在使用的资源。

         /// </summary>

         /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>

         protected override void Dispose(bool disposing)

         {

             if (disposing && (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.panel1 = new System.Windows.Forms.Panel();

             this.lb_ip = new System.Windows.Forms.Label();

             this.txt_ip = new System.Windows.Forms.TextBox();

             this.txt_port = new System.Windows.Forms.TextBox();

             this.lb_port = new System.Windows.Forms.Label();

             this.bt_connect = new System.Windows.Forms.Button();

             this.textBox1 = new System.Windows.Forms.TextBox();

             this.txt_msg = new System.Windows.Forms.TextBox();

             this.bt_send = new System.Windows.Forms.Button();

             this.panel1.SuspendLayout();

             this.SuspendLayout();

             //

             // panel1

             //

             this.panel1.Controls.Add(this.bt_connect);

             this.panel1.Controls.Add(this.txt_port);

             this.panel1.Controls.Add(this.lb_port);

             this.panel1.Controls.Add(this.txt_ip);

             this.panel1.Controls.Add(this.lb_ip);

             this.panel1.Location = new System.Drawing.Point(, );

             this.panel1.Name = "panel1";

             this.panel1.Size = new System.Drawing.Size(, );

             this.panel1.TabIndex = ;

             //

             // lb_ip

             //

             this.lb_ip.AutoSize = true;

             this.lb_ip.Location = new System.Drawing.Point(, );

             this.lb_ip.Name = "lb_ip";

             this.lb_ip.Size = new System.Drawing.Size(, );

             this.lb_ip.TabIndex = ;

             this.lb_ip.Text = "IP:";

             //

             // txt_ip

             //

             this.txt_ip.Location = new System.Drawing.Point(, );

             this.txt_ip.Name = "txt_ip";

             this.txt_ip.Size = new System.Drawing.Size(, );

             this.txt_ip.TabIndex = ;

             this.txt_ip.Text = "127.0.0.1";

             //

             // txt_port

             //

             this.txt_port.Location = new System.Drawing.Point(, );

             this.txt_port.Name = "txt_port";

             this.txt_port.Size = new System.Drawing.Size(, );

             this.txt_port.TabIndex = ;

             this.txt_port.Text = "";

             //

             // lb_port

             //

             this.lb_port.AutoSize = true;

             this.lb_port.Location = new System.Drawing.Point(, );

             this.lb_port.Name = "lb_port";

             this.lb_port.Size = new System.Drawing.Size(, );

             this.lb_port.TabIndex = ;

             this.lb_port.Text = "port:";

             //

             // bt_connect

             //

             this.bt_connect.Location = new System.Drawing.Point(, );

             this.bt_connect.Name = "bt_connect";

             this.bt_connect.Size = new System.Drawing.Size(, );

             this.bt_connect.TabIndex = ;

             this.bt_connect.Text = "连接";

             this.bt_connect.UseVisualStyleBackColor = true;

             this.bt_connect.Click += new System.EventHandler(this.bt_connect_Click);

             //

             // textBox1

             //

             this.textBox1.Location = new System.Drawing.Point(, );

             this.textBox1.Multiline = true;

             this.textBox1.Name = "textBox1";

             this.textBox1.Size = new System.Drawing.Size(, );

             this.textBox1.TabIndex = ;

             //

             // txt_msg

             //

             this.txt_msg.Location = new System.Drawing.Point(, );

             this.txt_msg.Multiline = true;

             this.txt_msg.Name = "txt_msg";

             this.txt_msg.Size = new System.Drawing.Size(, );

             this.txt_msg.TabIndex = ;

             //

             // bt_send

             //

             this.bt_send.Location = new System.Drawing.Point(, );

             this.bt_send.Name = "bt_send";

             this.bt_send.Size = new System.Drawing.Size(, );

             this.bt_send.TabIndex = ;

             this.bt_send.Text = "发送";

             this.bt_send.UseVisualStyleBackColor = true;

             this.bt_send.Click += new System.EventHandler(this.bt_send_Click);

             //

             // Form1

             //

             this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);

             this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;

             this.ClientSize = new System.Drawing.Size(, );

             this.Controls.Add(this.bt_send);

             this.Controls.Add(this.txt_msg);

             this.Controls.Add(this.textBox1);

             this.Controls.Add(this.panel1);

             this.Name = "Form1";

             this.Text = "Form1";

             this.Load += new System.EventHandler(this.Form1_Load);

             this.panel1.ResumeLayout(false);

             this.panel1.PerformLayout();

             this.ResumeLayout(false);

             this.PerformLayout();

         }

         #endregion

         private System.Windows.Forms.Panel panel1;

         private System.Windows.Forms.Label lb_ip;

         private System.Windows.Forms.Button bt_connect;

         private System.Windows.Forms.TextBox txt_port;

         private System.Windows.Forms.Label lb_port;

         private System.Windows.Forms.TextBox txt_ip;

         private System.Windows.Forms.TextBox textBox1;

         private System.Windows.Forms.TextBox txt_msg;

         private System.Windows.Forms.Button bt_send;

     }

 }

　　（2）客户端逻辑设计

 using System;

 using System.Collections.Generic;

 using System.ComponentModel;

 using System.Data;

 using System.Drawing;

 using System.Linq;

 using System.Net;

 using System.Net.Sockets;

 using System.Text;

 using System.Threading;

 using System.Windows.Forms;

 namespace SocketClient

 {

     public partial class Form1 : Form

     {

         public Form1()

         {

             InitializeComponent();

         }

         Socket socketSend;

         private void bt_connect_Click(object sender, EventArgs e)

         {

             try

             {

                 //创建客户端Socket，获得远程ip和端口号

                 socketSend = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

                 IPAddress ip = IPAddress.Parse(txt_ip.Text);

                 IPEndPoint point = new IPEndPoint(ip, Convert.ToInt32(txt_port.Text));

                 socketSend.Connect(point);

                 ShowMsg("连接成功!");

                 //开启新的线程，不停的接收服务器发来的消息

                 Thread c_thread = new Thread(Received);

                 c_thread.IsBackground = true;

                 c_thread.Start();

             }

             catch (Exception){

                 ShowMsg("IP或者端口号错误...");

             }

         }

         void ShowMsg(string str)

         {

             textBox1.AppendText(str + "\r\n");

         }

         /// <summary>

         /// 接收服务端返回的消息

         /// </summary>

         void Received()

         {

             while (true)

             {

                 try

                 {

                     byte[] buffer = new byte[ *  * ];

                     //实际接收到的有效字节数

                     int len = socketSend.Receive(buffer);

                     if (len == )

                     {

                         break;

                     }

                     string str = Encoding.UTF8.GetString(buffer, , len);

                     ShowMsg(socketSend.RemoteEndPoint + ":" + str);

                 }

                 catch { }

             }

         }

         /// <summary>

         /// 向服务器发送消息

         /// </summary>

         /// <param name="sender"></param>

         /// <param name="e"></param>

         private void bt_send_Click(object sender, EventArgs e)

         {

             try

             {

                 string msg = txt_msg.Text.Trim();

                 byte[] buffer = new byte[ *  * ];

                 buffer = Encoding.UTF8.GetBytes(msg);

                 socketSend.Send(buffer);

             }

             catch { }

         }

         private void Form1_Load(object sender, EventArgs e)

         {

             Control.CheckForIllegalCrossThreadCalls = false;

         }

     }

 }

七、运行效果

　　1、服务端

　　2、客户端

巴特西

SOCKET原理（转载）

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