构造.NET环境下的网页下载器 (2) | |||
作者: 王凯明 www.ASPCool.com 时间:2003-8-29 13:21:38 阅读次数:5358 | |||
最后,我就综合以上.NET网络编程的一些知识,向大家展示一个很好的实例。该实例是一个运用Socket的基于同步模式的客户端应用程序,它首先通过解析服务器的IP地址建立一个终结点,同时创建一个基于流套接字的Socket连接,其运用的协议是TCP协议。通过该Socket就可以发送获取网页的命令,再通过该Socket获得服务器上默认的网页,最后通过文件流将获得的数据写入本机文件。这样就完成了网页的下载工作了,程序运行的效果如下所示: ![]() 程序的代码如下: 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.Text; using System.IO; namespace SocketSample { /// <summary> /// Form1 的摘要说明。 /// </summary> public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.Label label1; private System.Windows.Forms.Label label2; private System.Windows.Forms.Button Download; private System.Windows.Forms.TextBox ServerAddress; private System.Windows.Forms.TextBox Filename; /// <summary> /// 必需的设计器变量。 /// </summary> private System.ComponentModel.Container components = null; public Form1() { // // 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 Form Designer generated code /// <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.Download = new System.Windows. Forms.Button(); this.ServerAddress = new System.Windows. Forms.TextBox(); this.Filename = new System.Windows. Forms.TextBox(); this.SuspendLayout(); // // label1 // this.label1.Location = new System.Drawing. Point(16, 24); this.label1.Name = "label1"; this.label1.Size = new System.Drawing. Size(80, 23); this.label1.TabIndex = 0; this.label1.Text = "服务器地址:"; this.label1.TextAlign = System.Drawing. ContentAlignment.MiddleRight; // // label2 // this.label2.Location = new System.Drawing. Point(16, 64); this.label2.Name = "label2"; this.label2.Size = new System.Drawing. Size(80, 23); this.label2.TabIndex = 1; this.label2.Text = "本地文件名:"; this.label2.TextAlign = System.Drawing. ContentAlignment.MiddleRight; // // Download // this.Download.Location = new System. Drawing.Point(288, 24); this.Download.Name = "Download"; this.Download.TabIndex = 2; this.Download.Text = "开始下载"; this.Download.Click += new System. EventHandler(this.Download_Click); // // ServerAddress // this.ServerAddress.Location = new System. Drawing.Point(96, 24); this.ServerAddress.Name = "ServerAddress"; this.ServerAddress.Size = new System. Drawing.Size(176, 21); this.ServerAddress.TabIndex = 3; this.ServerAddress.Text = ""; // // Filename // this.Filename.Location = new System. Drawing.Point(96, 64); this.Filename.Name = "Filename"; this.Filename.Size = new System. Drawing.Size(176, 21); this.Filename.TabIndex = 4; this.Filename.Text = ""; // // Form1 // this.AutoScaleBaseSize = new System. Drawing.Size(6, 14); this.ClientSize = new System.Drawing. Size(376, 117); this.Controls.AddRange(new System.Windows. Forms.Control[] { this.Filename, this.ServerAddress, this.Download, this.label2, this.label1}); this.Name = "Form1"; this.Text = "网页下载器"; this.ResumeLayout(false); } #endregion /// <summary> /// 应用程序的主入口点。 /// </summary> [STAThread] static void Main() { Application.Run(new Form1()); } private string DoSocketGet(string server) { //定义一些必要的变量以及一条要发送到服务器的字符串 Encoding ASCII = Encoding.ASCII; string Get = "GET / HTTP/1.1/r/nHost: " +server+"/r/nConnection: Close/r/n/r/n"; Byte[] ByteGet = ASCII.GetBytes(Get); Byte[] RecvBytes = new Byte[256]; String strRetPage = null; //获取服务器相关的IP地址列表,其中第一项即为我们所需的 IPAddress hostadd = Dns.Resolve(server). AddressList[0]; //根据获得的服务器的IP地址创建一个终结点,端口为默认的80 IPEndPoint EPhost = new IPEndPoint (hostadd, 80); //创建一个Socket实例 Socket s = new Socket(AddressFamily. InterNetwork, SocketType.Stream, ProtocolType.Tcp ); try { //用上面所取得的终结点连接到服务器 s.Connect(EPhost); } catch(Exception se) { MessageBox.Show("连接错误:"+se. Message,"提示信息",MessageBoxButtons. RetryCancel,MessageBoxIcon.Information); } if (!s.Connected) { strRetPage = "不能连接到服务器!"; return strRetPage; } try { //向服务器发送GET命令 s.Send(ByteGet, ByteGet.Length, SocketFlags.None); } catch(Exception ce) { MessageBox.Show("发送错误:"+ce. Message,"提示信息",MessageBoxButtons. RetryCancel,MessageBoxIcon.Information); } //接收页面数据,直到所有字节接收完毕 Int32 bytes = s.Receive(RecvBytes, RecvBytes.Length, 0); strRetPage = "以下是在服务器" + server + "上的默认网页:/r/n"; strRetPage = strRetPage + ASCII.GetString (RecvBytes, 0, bytes); while (bytes > 0) { bytes = s.Receive(RecvBytes, RecvBytes.Length, SocketFlags.None); strRetPage = strRetPage + ASCII. GetString(RecvBytes, 0, bytes); } //禁用并关闭Socket实例 s.Shutdown(SocketShutdown.Both); s.Close(); return strRetPage; } private void Download_Click(object sender, System. EventArgs e) { //将所读取的字符串转换为字节数组 byte[] content=Encoding.ASCII.GetBytes (DoSocketGet(ServerAddress.Text)); try { //创建文件流对象实例 FileStream fs=new FileStream (Filename.Text,FileMode.OpenOrCreate,FileAccess. ReadWrite); //写入文件 fs.Write(content,0,content.Length); } catch(Exception fe) { MessageBox.Show("文件创建/写入错误: "+fe.Message,"提示信息",MessageBoxButtons. RetryCancel,MessageBoxIcon.Information); } } } } 其中主要的函数为DoSocketGet(),首先程序在响应"开始下载"的事件处理函数Download_Click(),调用DoSocketGet()函数,该函数完成了套接字的创建、连接、与主机的通讯-即获得主机上的网页、禁用、关闭等功能。在调用完DoSocketGet()函数后,Download_Click()函数创建一个FileStream对象,并试图将DoSocketGet()函数返回的网页文件以字节数组的形式写到本机文件中,最终形成在本机上的一个Html文件,这样就完成了一个网页文件的下载工作了。 不过这个程序的功能比较简单,不能作为真正的网页浏览器用,网页文件下载后还是要用IE等浏览器才能打开。然而作为一个解释.NET底层网络编程的实例绝对是一个好例子,所以希望读者能好好研究,同时读者还可以添加文件下载进度条等以完善本程序。 注:以上程序在Windows 2000服务器版、Visual Studio.Net中文正式版下调试通过 |