| 導購 | 订阅 | 在线投稿
分享
 
 
 

Java網絡編程基礎(四) ServerSocket類使用

來源:互聯網  2008-10-30 08:14:21  評論

由于SSClient使用了流套接字,所以服務程序也要使用流套接字。

這就要創建一個ServerSocket對象,ServerSocket有幾個構造函數,最簡單的是ServerSocket(int port),當使用ServerSocket(int port)創建一個ServerSocket對象,port參數傳遞端口號,這個端口就是服務器監聽連接請求的端口,如果在這時出現錯誤將抛出IOException異常對象,否則將創建ServerSocket對象並開始准備接收連接請求。

接下來服務程序進入無限循環之中,無限循環從調用ServerSocket的accept()方法開始,在調用開始後accept()方法將導致調用線程阻塞直到連接建立。在建立連接後accept()返回一個最近創建的Socket對象,該Socket對象綁定了客戶程序的IP地址或端口號。

由于存在單個服務程序與多個客戶程序通訊的可能,所以服務程序響應客戶程序不應該花很多時間,否則客戶程序在得到服務前有可能花很多時間來等待通訊的建立,然而服務程序和客戶程序的會話有可能是很長的(這與電話類似),因此爲加快對客戶程序連接請求的響應,典型的方法是服務器主機運行一個後台線程,這個後台線程處理服務程序和客戶程序的通訊。

爲了示範我們在上面談到的慨念並完成SSClient程序,下面我們創建一個SSServer程序,程序將創建一個ServerSocket對象來監聽端口10000的連接請求,如果成功服務程序將等待連接輸入,開始一個線程處理連接,並響應來自客戶程序的命令。下面就是這段程序的代碼:

Listing 3: SSServer.java

// SSServer.java

import java.io.*;

import java.net.*;

import java.util.*;

class SSServer

{

public static void main (String [] args) throws IOException

{

System.out.println ("Server starting...\n");

// Create a server socket that listens for incoming connection

// requests on port 10000.

ServerSocket server = new ServerSocket (10000);

while (true)

{

// Listen for incoming connection requests from client

// programs, establish a connection, and return a Socket

// object that redivsents this connection.

Socket s = server.accept ();

System.out.println ("Accepting Connection...\n");

// Start a thread to handle the connection.

new ServerThread (s).start ();

}

}

}

class ServerThread extends Thread

{

private Socket s;

ServerThread (Socket s)

{

this.s = s;

}

public void run ()

{

BufferedReader br = null;

PrintWriter pw = null;

try

{

// Create an input stream reader that chains to the socket's

// byte-oriented input stream. The input stream reader

// converts bytes read from the socket to characters. The

// conversion is based on the platform's default character

// set.

InputStreamReader isr;

isr = new InputStreamReader (s.getInputStream ());

// Create a buffered reader that chains to the input stream

// reader. The buffered reader supplies a convenient method

// for reading entire lines of text.

br = new BufferedReader (isr);

// Create a print writer that chains to the socket's byte-

// oriented output stream. The print writer creates an

// intermediate output stream writer that converts

// characters sent to the socket to bytes. The conversion

// is based on the platform's default character set.

pw = new PrintWriter (s.getOutputStream (), true);

// Create a calendar that makes it possible to obtain date

// and time information.

Calendar c = Calendar.getInstance ();

// Because the client program may send multiple commands, a

// loop is required. Keep looping until the client either

// explicitly requests termination by sending a command

// beginning with letters BYE or implicitly requests

// termination by closing its output stream.

do

{

// Obtain the client program's next command.

String cmd = br.readLine ();

// Exit if client program has closed its output stream.

if (cmd == null)

break;

// Convert command to uppercase, for ease of comparison.

cmd = cmd.toUpperCase ();

// If client program sends BYE command, terminate.

if (cmd.startsWith ("BYE"))

break;

// If client program sends DATE or TIME command, return

// current date/time to the client program.

if (cmd.startsWith ("DATE") || cmd.startsWith ("TIME"))

pw.println (c.getTime ().toString ());

// If client program sends DOM (Day Of Month) command,

// return current day of month to the client program.

if (cmd.startsWith ("DOM"))

pw.println ("" + c.get (Calendar.DAY_OF_MONTH));

// If client program sends DOW (Day Of Week) command,

// return current weekday (as a string) to the client

// program.

if (cmd.startsWith ("DOW"))

switch (c.get (Calendar.DAY_OF_WEEK))

{

case Calendar.SUNDAY : pw.println ("SUNDAY");

break;

case Calendar.MONDAY : pw.println ("MONDAY");

break;

case Calendar.TUESDAY : pw.println ("TUESDAY");

break;

case Calendar.WEDNESDAY: pw.println ("WEDNESDAY");

break;

case Calendar.THURSDAY : pw.println ("THURSDAY");

break;

case Calendar.FRIDAY : pw.println ("FRIDAY");

break;

case Calendar.SATURDAY : pw.println ("SATURDAY");

}

// If client program sends DOY (Day of Year) command,

// return current day of year to the client program.

if (cmd.startsWith ("DOY"))

pw.println ("" + c.get (Calendar.DAY_OF_YEAR));

// If client program sends PAUSE command, sleep for three

// seconds.

if (cmd.startsWith ("PAUSE"))

try

{

Thread.sleep (3000);

}

catch (InterruptedException e)

{

}

}

while (true);

{

catch (IOException e)

{

System.out.println (e.toString ());

}

finally

{

System.out.println ("Closing Connection...\n");

try

{

if (br != null)

br.close ();

if (pw != null)

pw.close ();

if (s != null)

s.close ();

}

catch (IOException e)

{

}

}

}

}

運行這段程序將得到下面的輸出:

Server starting...

Accepting Connection...

Closing Connection...

SSServer的源代碼聲明了一對類:SSServer 和ServerThread;SSServer的main()方法創建了一個ServerSocket對象來監聽端口10000上的連接請求,如果成功, SSServer進入一個無限循環中,交替調用ServerSocket的 accept() 方法來等待連接請求,同時啓動後台線程處理連接(accept()返回的請求)。線程由ServerThread繼承的start()方法開始,並執行ServerThread的run()方法中的代碼。

一旦run()方法運行,線程將創建BufferedReader, PrintWriter和 Calendar對象並進入一個循環,這個循環由讀(通過BufferedReader的 readLine())來自客戶程序的一行文本開始,文本(命令)存儲在cmd引用的string對象中,如果客戶程序過早的關閉輸出流,會發生什麽呢?答案是:cmd將得不到賦值。

注意必須考慮到這種情況:在服務程序正在讀輸入流時,客戶程序關閉了輸出流,如果沒有對這種情況進行處理,那麽程序將産生異常。

一旦編譯了SSServer的源代碼,通過輸入Java SSServer來運行程序,在開始運行SSServer後,就可以運行一個或多個SSClient程序。

由于SSClient使用了流套接字,所以服務程序也要使用流套接字。 這就要創建一個ServerSocket對象,ServerSocket有幾個構造函數,最簡單的是ServerSocket(int port),當使用ServerSocket(int port)創建一個ServerSocket對象,port參數傳遞端口號,這個端口就是服務器監聽連接請求的端口,如果在這時出現錯誤將抛出IOException異常對象,否則將創建ServerSocket對象並開始准備接收連接請求。 接下來服務程序進入無限循環之中,無限循環從調用ServerSocket的accept()方法開始,在調用開始後accept()方法將導致調用線程阻塞直到連接建立。在建立連接後accept()返回一個最近創建的Socket對象,該Socket對象綁定了客戶程序的IP地址或端口號。 由于存在單個服務程序與多個客戶程序通訊的可能,所以服務程序響應客戶程序不應該花很多時間,否則客戶程序在得到服務前有可能花很多時間來等待通訊的建立,然而服務程序和客戶程序的會話有可能是很長的(這與電話類似),因此爲加快對客戶程序連接請求的響應,典型的方法是服務器主機運行一個後台線程,這個後台線程處理服務程序和客戶程序的通訊。 爲了示範我們在上面談到的慨念並完成SSClient程序,下面我們創建一個SSServer程序,程序將創建一個ServerSocket對象來監聽端口10000的連接請求,如果成功服務程序將等待連接輸入,開始一個線程處理連接,並響應來自客戶程序的命令。下面就是這段程序的代碼: Listing 3: SSServer.java // SSServer.java import java.io.*; import java.net.*; import java.util.*; class SSServer {  public static void main (String [] args) throws IOException  {    System.out.println ("Server starting...\n");   // Create a server socket that listens for incoming connection   // requests on port 10000.   ServerSocket server = new ServerSocket (10000);   while (true)   {    // Listen for incoming connection requests from client    // programs, establish a connection, and return a Socket    // object that redivsents this connection.    Socket s = server.accept ();    System.out.println ("Accepting Connection...\n");    // Start a thread to handle the connection.    new ServerThread (s).start ();   }  } } class ServerThread extends Thread {  private Socket s;  ServerThread (Socket s)  {   this.s = s;  }  public void run ()  {   BufferedReader br = null;   PrintWriter pw = null;   try   {    // Create an input stream reader that chains to the socket's    // byte-oriented input stream. The input stream reader    // converts bytes read from the socket to characters. The    // conversion is based on the platform's default character    // set.    InputStreamReader isr;    isr = new InputStreamReader (s.getInputStream ());    // Create a buffered reader that chains to the input stream    // reader. The buffered reader supplies a convenient method    // for reading entire lines of text.    br = new BufferedReader (isr);    // Create a print writer that chains to the socket's byte-    // oriented output stream. The print writer creates an    // intermediate output stream writer that converts    // characters sent to the socket to bytes. The conversion    // is based on the platform's default character set.    pw = new PrintWriter (s.getOutputStream (), true);    // Create a calendar that makes it possible to obtain date    // and time information.    Calendar c = Calendar.getInstance ();  // Because the client program may send multiple commands, a    // loop is required. Keep looping until the client either    // explicitly requests termination by sending a command    // beginning with letters BYE or implicitly requests    // termination by closing its output stream.    do    {     // Obtain the client program's next command.     String cmd = br.readLine ();     // Exit if client program has closed its output stream.     if (cmd == null)      break;        // Convert command to uppercase, for ease of comparison.     cmd = cmd.toUpperCase ();     // If client program sends BYE command, terminate.     if (cmd.startsWith ("BYE"))      break;     // If client program sends DATE or TIME command, return     // current date/time to the client program.     if (cmd.startsWith ("DATE") || cmd.startsWith ("TIME"))      pw.println (c.getTime ().toString ());     // If client program sends DOM (Day Of Month) command,     // return current day of month to the client program.     if (cmd.startsWith ("DOM"))      pw.println ("" + c.get (Calendar.DAY_OF_MONTH));     // If client program sends DOW (Day Of Week) command,     // return current weekday (as a string) to the client     // program.     if (cmd.startsWith ("DOW"))      switch (c.get (Calendar.DAY_OF_WEEK))  {      case Calendar.SUNDAY : pw.println ("SUNDAY");       break;      case Calendar.MONDAY : pw.println ("MONDAY");       break;      case Calendar.TUESDAY : pw.println ("TUESDAY");       break;      case Calendar.WEDNESDAY: pw.println ("WEDNESDAY");       break;      case Calendar.THURSDAY : pw.println ("THURSDAY");       break;      case Calendar.FRIDAY : pw.println ("FRIDAY");       break;      case Calendar.SATURDAY : pw.println ("SATURDAY");     }     // If client program sends DOY (Day of Year) command,     // return current day of year to the client program.     if (cmd.startsWith ("DOY"))      pw.println ("" + c.get (Calendar.DAY_OF_YEAR));      // If client program sends PAUSE command, sleep for three      // seconds.       if (cmd.startsWith ("PAUSE"))     try     {      Thread.sleep (3000);     }     catch (InterruptedException e)     {     }    }    while (true);    {    catch (IOException e)    {        System.out.println (e.toString ());    }    finally    {     System.out.println ("Closing Connection...\n");     try     {      if (br != null)       br.close ();       if (pw != null)        pw.close ();       if (s != null)        s.close ();     }     catch (IOException e)     {     }    }   } } 運行這段程序將得到下面的輸出: Server starting... Accepting Connection... Closing Connection... SSServer的源代碼聲明了一對類:SSServer 和ServerThread;SSServer的main()方法創建了一個ServerSocket對象來監聽端口10000上的連接請求,如果成功, SSServer進入一個無限循環中,交替調用ServerSocket的 accept() 方法來等待連接請求,同時啓動後台線程處理連接(accept()返回的請求)。線程由ServerThread繼承的start()方法開始,並執行ServerThread的run()方法中的代碼。 一旦run()方法運行,線程將創建BufferedReader, PrintWriter和 Calendar對象並進入一個循環,這個循環由讀(通過BufferedReader的 readLine())來自客戶程序的一行文本開始,文本(命令)存儲在cmd引用的string對象中,如果客戶程序過早的關閉輸出流,會發生什麽呢?答案是:cmd將得不到賦值。 注意必須考慮到這種情況:在服務程序正在讀輸入流時,客戶程序關閉了輸出流,如果沒有對這種情況進行處理,那麽程序將産生異常。 一旦編譯了SSServer的源代碼,通過輸入Java SSServer來運行程序,在開始運行SSServer後,就可以運行一個或多個SSClient程序。
󰈣󰈤
王朝萬家燈火計劃
期待原創作者加盟
 
 
 
>>返回首頁<<
 
 
 
 
 熱帖排行
 
 
 
靜靜地坐在廢墟上,四周的荒凉一望無際,忽然覺得,淒涼也很美
© 2005- 王朝網路 版權所有