12.并以下面代碼替換Form.cs中由系統產生的InitializeComponent過程。

PRivate void InitializeComponent ( ){this.button1 = new System.Windows.Forms.Button ( ) ;this.button2 = new System.Windows.Forms.Button ( ) ;this.textBox1 = new System.Windows.Forms.TextBox ( ) ;this.textBox2 = new System.Windows.Forms.TextBox ( ) ;this.label1 = new System.Windows.Forms.Label ( ) ;this.label2 = new System.Windows.Forms.Label ( ) ;this.label3 = new System.Windows.Forms.Label ( ) ;this.textBox3 = new System.Windows.Forms.TextBox ( ) ;this.SuspendLayout ( ) ;this.button1.FlatStyle = System.Windows.Forms.FlatStyle.Flat ;this.button1.Location = new System.Drawing.Point ( 128 , 128 ) ;this.button1.Name = "button1" ;this.button1.Size = new System.Drawing.Size ( 112 , 40 ) ;this.button1.TabIndex = 0 ;this.button1.Text = "獲取" ;this.button1.Click += new System.EventHandler ( this.button1_Click ) ;this.button2.FlatStyle = System.Windows.Forms.FlatStyle.Flat ;this.button2.Location = new System.Drawing.Point ( 128 , 184 ) ;this.button2.Name = "button2" ;this.button2.Size = new System.Drawing.Size ( 112 , 40 ) ;this.button2.TabIndex = 1 ;this.button2.Text = "對時" ;this.button2.Click += new System.EventHandler ( this.button2_Click ) ;this.textBox1.Location = new System.Drawing.Point ( 120 , 56 ) ;this.textBox1.Name = "textBox1" ;this.textBox1.Size = new System.Drawing.Size ( 200 , 21 ) ;this.textBox1.TabIndex = 2 ;this.textBox1.Text = "" ;this.textBox2.Location = new System.Drawing.Point ( 120 , 88 ) ;this.textBox2.Name = "textBox2" ;this.textBox2.Size = new System.Drawing.Size ( 200 , 21 ) ;this.textBox2.TabIndex = 3 ;this.textBox2.Text = "" ;this.label1.Location = new System.Drawing.Point ( 48 , 56 ) ;this.label1.Name = "label1" ;this.label1.TabIndex = 4 ;this.label1.Text = "本地時間：" ;this.label2.Location = new System.Drawing.Point ( 40 , 88 ) ;this.label2.Name = "label2" ;this.label2.Size = new System.Drawing.Size ( 88 , 24 ) ;this.label2.TabIndex = 5 ;this.label2.Text = "服務器時間：" ;this.label3.Location = new System.Drawing.Point ( 16 , 24 ) ;this.label3.Name = "label3" ;this.label3.Size = new System.Drawing.Size ( 112 , 23 ) ;this.label3.TabIndex = 6 ;this.label3.Text = "設定服務器地址：" ;this.textBox3.Location = new System.Drawing.Point ( 120 , 24 ) ;this.textBox3.Name = "textBox3" ;this.textBox3.Size = new System.Drawing.Size ( 200 , 21 ) ;this.textBox3.TabIndex = 7 ;this.textBox3.Text = "" ;this.AutoScaleBaseSize = new System.Drawing.Size ( 6 , 14 ) ;this.ClientSize = new System.Drawing.Size ( 352 , 245 ) ;this.Controls.AddRange ( new System.Windows.Forms.Control[] {   this.textBox3 ,   this.textBox2 ,   this.textBox1 ,   this.button2 ,   this.button1 ,   this.label1 ,   this.label2 ,   this.label3} ) ;this.MaximizeBox = false ;this.Name = "Form1" ;this.Text = "UDP對時客戶端" ;this.ResumeLayout ( false ) ;}

13.在Form1.cs中的InitializeComponent過程之后，添加下列代碼，下列代碼的功能是在程序中導入WinAPI函數——SetSystemTime，這個函數位于文件Kernel32.dll。程序就是通過此函數來更正系統時間的。

[ DllImport (  "Kernel32.dll"  )]private static extern bool SetSystemTime (  SystemTime time ) ;//引入API函數

{ client = new UdpClient ( port ) ; ipAddress a = IPAddress.Parse  ( "127001" ) ; receivePoint = new IPEndPoint ( a  , port ) ; IPAddress HostIP ; bool continueLoop = true ; while ( continueLoop ) { string hostName = Dns.GetHostName ( ) ; System.Text.ASCIIEncoding encode           = new System.Text.ASCIIEncoding ( ) ; //定義發送到服務器端的請求信息 //請求信息是一個字符串，為客戶端名稱和接收服務器反饋信息的端口號組成的字符串 string sendString = hostName + "/" + port.ToString ( ) ; byte[] sendData = encode.GetBytes ( sendString ) ; //判定使用者輸入的是IP地址還是計算機名稱 try {  HostIP = IPAddress.Parse  ( textBox3.Text ) ; } catch {  //假如輸入的是計算機名稱，則按照執行下列代碼。  //發送請求信息  client.Send ( sendData , sendData.                   Length , textBox3.Text , 8080 ) ;  //接收來自服務器端的信息   byte[] recData =                            client.Receive ( ref receivePoint ) ;  timeString = encode.GetString ( recData ) ;  client.Close ( ) ;  continueLoop=false ;      return ; } //輸入的是IP地址，則執行下列代碼 IPEndPoint host = new IPEndPoint ( HostIP ,8080 ) ; //發送請求信息 client.Send ( sendData , sendData.Length , host ) ; //接收來自服務器端的信息 byte[] recData1 = client.Receive ( ref receivePoint ) ; //獲取服務器端的時間和日期 timeString = encode.GetString ( recData1 ) ; client.Close ( ) ; //退出循環 continueLoop=false ;    }}

private void button1_Click ( object sender , System.EventArgs e ){ start_client ( ) ; textBox1.Text = DateTime.Now.ToString ( ) ; //顯示客戶端當前時間和日期 textBox2.Text = timeString ; //顯示服務器當前時間和日期}

private void button2_Click ( object sender , System.EventArgs e ){ start_client ( ) ; //把接收來的數據轉換時間日期格式 try {  temp = DateTime.Parse  ( timeString ) ; } catch {  MessageBox.Show  ( "錯誤時間" ) ;  return ; } //根據得到的時間日期，來定義時間、日期 SystemTime st= new SystemTime ( ) ; st.year=  ( short )temp.Year ; st.Month= ( short )temp.Month ; st.DayOfWeek= ( short )temp.DayOfWeek ; st.Day= ( short )temp.Day ; st.Hour=Convert.ToInt16 ( temp.Hour ) ; if ( st.Hour>=12 ) {  st.Hour-= ( short )8 ; } else if ( st.Hour >= 8 ) {  st.Hour-= ( short )8 ; } else {  st.Hour+= ( short )16 ; } st.Minute=Convert.ToInt16 ( temp.Minute ) ; st.Second=Convert.ToInt16 ( temp.Second ) ; st.Milliseconds=Convert.ToInt16 ( temp.Millisecond ) ; //修改本地端的時間和日期 if ( SetSystemTime ( st ) ) { MessageBox.Show ( DateTime.Now.ToString ( ) ,"修改成功" ) ; }  else MessageBox.Show ( "不成功！" ,"不成功" ) ;}

七．總結：

本文具體介紹了UDP協議，.Net FrameWork SDK提供給Visual C＃用以操作UDP協議的主要類庫，以及通過一個具體而使用的示例——實現一個網絡對時系統，介紹在Visual C＃實現UDP協議的具體方法和過程。UDP由于其自身的缺點注定在某些領域無法利用它，但在可以利用它的領域，UDP以其快捷、簡單、實用的特點正在受到更多程序員的歡迎。尤其在現代，網絡運行態勢越來越好的情況下，可以預見的是UDP在網絡中的應用情景將更廣闊。希望本文的內容對您把握用Visual C＃編寫基于UDP的網絡應用程序有所幫助。