usetimeserver.java

实现Time服务器的java程序

import java.net.*;
import java.io.*;
import java.util.Date;
 
public class useTimeServer 
{ 
	//设置常数属性
  	public final static int DEFAULT_PORT = 37;
	
	//主程序
  	public static void main(String[] args) 
  	{        
  		//设置缺省端口
   		int port = DEFAULT_PORT;     
   		if (args.length > 0) 
   		{
     			try 
     			{
     				//从参数中获取端口信息
        			port = Integer.parseInt(args[0]);
        			//判断端口输入是否正确
        			if (port < 0 || port >= 65536) 
        			{
          				System.out.println("Port must between 0 and 65535");
          				return;      
        			}
     			}   
     			//捕获异常
     			catch (NumberFormatException e) {}  
   		}     

   		// 时间协议设置从1900年开始纪年
   		//java Date类从1970年开始纪年 
   		// 在当中要进行数量转换
    		//设置转换常量
   		long differenceBetweenEpochs = 2208988800L;
    
   		try 
   		{
   			//建立ServerSocket
     			ServerSocket server = new ServerSocket(port);
     			//服务一直运行
       			while (true) 
       			{
       				Socket connection = null;
         			try 
         			{
         				//建立Socket连接
           				connection = server.accept();
           				//建立输出流对象
           				OutputStream out = connection.getOutputStream();
           				//新建时间对象
           				Date now = new Date();
           				//获取时间
           				long msSince1970 = now.getTime();
           				long secondsSince1970 = msSince1970/1000;
           				//处理纪年差异
           				long secondsSince1900 = secondsSince1970+ differenceBetweenEpochs;
           				//获取符合Time协议的时间值
           				byte[] time = new byte[4];
           				time[0]= (byte) ((secondsSince1900 & 0x00000000FF000000L) >> 24);
           				time[1]= (byte) ((secondsSince1900 & 0x0000000000FF0000L) >> 16);
           				time[2]= (byte) ((secondsSince1900 & 0x000000000000FF00L) >> 8);
           				time[3] = (byte) (secondsSince1900 & 0x00000000000000FFL);
           				//输出时间值
           				out.write(time);
           				out.flush();      
         			} // end try
         			catch (IOException e) 
         			{} // end catch
         			finally 
         			{
         				//关闭连接
           				if (connection != null) connection.close(); 
         			}
       			}  // end while
   		}  // end try
   		catch (IOException e) 
   		{
     			System.err.println(e);
   		} // end catch

  	} // end main

} // end useTimeServer