eadf.txt

模拟ethernet帧的发送过程

 * @(#)Ethernet.java
 *function :模拟帧的发送过程
 *
 * @author :seaman
 * @version 1.00 

import java.util.* ;
import java.lang.Math.* ;

public class Ethernet extends Thread
{
	static long Bus=0;
	static int CollisionCounter = 20;				//最大重试次数
	static double collisionWindow = 0.005;	                        //冲突窗口大小
	static int randNum = (int)(100 * Math.random() % 3 );		//随机数

	public static void main(String args[])
	{
		A_Host	a = new A_Host() ;
		B_Host  b = new B_Host() ;

		A_Host.ID1 = a.getId() ;
		a.start() ;
		B_Host.ID2 = b.getId() ;
		b.start() ;
	}

}

class A_Host extends Thread
{
	static long ID1 ;						  //线程a的线程标示
	int times_a = 0 ;						  //发送成功次数计数器
	int CollisionCounter =20;					  //冲突计数器最大计数初值为20

	public void run()
	{
		A_send() ;
	}

	public boolean A_send()
	{
		boolean flg = false ;					 //发送成功标志
	 	Ethernet.Bus= Ethernet.Bus| ID1;		         //模拟数据发送
		try
		{
	 		sleep(15);					 //休眠15毫秒
		}
		catch(InterruptedException e)
		{
			System.out.println("线程A休眠发生错误!");
		}

	 	if(Ethernet.Bus == ID1)					 //无冲突
	 	{
	 	 	 System.out.println(ID1 + " ID Send Success ");
	 	 	 flg = true ;
			 Ethernet.Bus=0;				 //发送成功后之总线空闲
			 CollisionCounter = 20;				 //恢复冲突计数器的内容
			 try
			 {
			 	sleep((int)(100 * Math.random() % 10));	 //随机延时
			 }
			 catch(InterruptedException e)
			 {
			 		System.out.println("线程A休眠发生错误!");
			 }
			 times_a ++;					 //发送成功次数加1
			 System.out.println("主机a发送成功次数= " + times_a);

			 while ( times_a < 10)				 //发送成功次数不足十次时，继续发送
			 {
			 	A_send() ;
			 }

		 }
		 else							 //有冲突时
		 {
			 System.out.println(ID1 + " ID Send Collision " + (17 - CollisionCounter) + "次");
			 Ethernet.Bus = 0;				//产生冲突后，置总线空闲
			 CollisionCounter --;				//冲突计数器内容减1
			 if(CollisionCounter > 0)
			 {
			 	 int temp =(int) Math.pow( 2.0,(CollisionCounter>10)?10.0:(double)CollisionCounter );
				 try
				 {
					                               //截止二进制指数退避算法延时
				 	sleep(Ethernet.randNum * temp * (int)(Ethernet.collisionWindow * 10) );	
				 	sleep(Ethernet.randNum*(int)Math.pow(2,(CollisionCounter > 10)?10:CollisionCounter) * Ethernet.collisionWindow) ;
				 }
				 catch(InterruptedException e)
				 {
				 	System.out.println("线程A休眠发生错误!");
				 }
				 A_send() ;					//尝试重新发送数据
			 }
			 else
			 {
			 	 System.out.println(ID1 + "ID Send Failuer ");	//发送失败！
				 flg = false ;
			 }
		 }
		 return flg ;
	 }
}

class B_Host extends Thread
{
	static	long ID2 ;
	int times_b = 0 ;
	int CollisionCounter =20 ;

	public void run()
	{
		B_send() ;
	}

	public boolean B_send()
	{
		boolean flg = false ;
	 	Ethernet.Bus= Ethernet.Bus| ID2;		//模拟数据发送
		try
		{
	 		sleep(10);
		}
		catch(InterruptedException e)
		{
			System.out.println("线程B休眠发生错误!");
		}

	 	if(Ethernet.Bus == ID2)		                //无冲突
	 	{  
	 	 	 System.out.println(ID2 + " ID Send Success ");
	 	 	 flg = true ;
			 Ethernet.Bus=0;
			 CollisionCounter = 20;		        //恢复冲突计数器的内容
			 try
			 {
			 	sleep((int)(100 * Math.random() % 10));	 //随机延时
			 }
			 catch(InterruptedException e)
			 {
			 		System.out.println("线程B休眠发生错误!");
			 }
			 times_b ++;					//发送成功次数加1
			 System.out.println("主机b发送成功次数= " + times_b);

			 while ( times_b < 10)		        //发送成功次数不足十次时，继续发送
			 {
			 	B_send() ;
			 }

		 }
		 else			                       //有冲突
		 {
			 System.out.println(ID2 + "ID Send Collision "+ (17-CollisionCounter) + "次");
			 Ethernet.Bus= 0;
			 CollisionCounter --;
			 if(CollisionCounter > 0)
			 {      //二进制退避算法延时
			 	 int temp =(int) Math.pow( 2.0,(CollisionCounter>10)?10.0:(double)CollisionCounter );
				 try
				 {
				 	sleep(Ethernet.randNum * temp * (int)(Ethernet.collisionWindow * 10) );
				 	sleep(Ethernet.randNum*(int)Math.pow(2,(CollisionCounter > 10)?10:CollisionCounter) * Ethernet.collisionWindow) ;
				 }
				 catch(InterruptedException e)
				 {
				 	System.out.println("线程A休眠发生错误!");
				 }
				 B_send() ;
			 }
			 else
			 {
			 	 System.out.println(ID2 + "ID Send Failuer ");
				 flg = false ;
			 }
		 }
		 return flg ;
	 }

}

}