Java的ServerSocket类怎么用

本篇内容主要讲解“Java的ServerSocket类怎么用”,感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷,实用性强。下面就让小编来带大家学习“Java的ServerSocket类怎么用”吧!

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ServerSocket类

由于SSClient使用了流套接字,所以服务程序也要使用流套接字。这就要创建一个ServerSocket对象,ServerSocket有几个构造函数,最简单的是ServerSocket(int port),当使用ServerSocket(int port)创建一个ServerSocket对象,port参数传递端口号,这个端口就是服务器监听连接请求的端口,如果在这时出现错误将抛出IOException异常对象,否则将创建ServerSocket对象并开始准备接收连接请求。

接下来服务程序进入无限循环之中,无限循环从调用ServerSocket的accept()方法开始,在调用开始后accept()方法将导致调用线程阻塞直到连接建立。在建立连接后accept()返回一个最近创建的Socket对象,该Socket对象绑定了客户程序的IP地址或端口号。

由于存在单个服务程序与多个客户程序通讯的可能,所以服务程序响应客户程序不应该花很多时间,否则客户程序在得到服务前有可能花很多时间来等待通讯的建立,然而服务程序和客户程序的会话有可能是很长的(这与电话类似),因此为加快对客户程序连接请求的响应,典型的方法是服务器主机运行一个后台线程,这个后台线程处理服务程序和客户程序的通讯。

为了示范我们在上面谈到的慨念并完成SSClient程序,下面我们创建一个SSServer程序,程序将创建一个ServerSocket对象来监听端口10000的连接请求,如果成功服务程序将等待连接输入,开始一个线程处理连接,并响应来自客户程序的命令。下面就是这段程序的代码:

Listing 3: SSServer.JavaXML:namespace prefix = o ns = "urn:schemas-microsoft-com:Office:office" />

// 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 represents 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)
  {
  }
 }
}
}


运行这段程序将得到下面的输出:

Server starting...
Accepting Connection...
Closing Connection...


SSServer的源代码声明了一对类:SSServer 和ServerThread;SSServer的main()方法创建了一个ServerSocket对象来监听端口10000上的连接请求,如果成功, SSServer进入一个无限循环中,交替调用ServerSocket的 accept() 方法来等待连接请求,同时启动后台线程处理连接(accept()返回的请求)。线程由ServerThread继承的start()方法开始,并执行ServerThread的run()方法中的代码。

一旦run()方法运行,线程将创建BufferedReader, PrintWriter和 Calendar对象并进入一个循环,这个循环由读(通过BufferedReader的 readLine())来自客户程序的一行文本开始,文本(命令)存储在cmd引用的string对象中,如果客户程序过早的关闭输出流,会发生什么呢?答案是:cmd将得不到赋值。

注意必须考虑到这种情况:在服务程序正在读输入流时,客户程序关闭了输出流,如果没有对这种情况进行处理,那么程序将产生异常。

一旦编译了SSServer的源代码,通过输入Java SSServer来运行程序,在开始运行SSServer后,就可以运行一个或多个SSClient程序。

到此,相信大家对“Java的ServerSocket类怎么用”有了更深的了解,不妨来实际操作一番吧!这里是创新互联网站,更多相关内容可以进入相关频道进行查询,关注我们,继续学习!


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