jie.java

网络的停止等待ARQ的模拟

import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
class Se extends Frame
{ 
  TextField tf=new TextField(10);
  TextArea ta=new TextArea(5,10);
  Socket c;
  public Se()
  {
   super("接收方");
   setSize(250,250);
   ServerSocket sever=null;
   Socket you=null;
   String s=null;
   DataOutputStream out=null;
   DataInputStream in=null;
   double m1,m2;
   String s1,s2,s3;
   s1="";s2="";s3="";
   int i=0;
   int q=0;
   int n;
   add("North",tf);
   add("Center",ta);
   addWindowListener(new WindowAdapter(){public void windowClosing(WindowEvent e){System.exit(0);}});
   show();
   try
   {
    sever=new ServerSocket(8888);
    you=sever.accept();
	
	in=new DataInputStream(you.getInputStream());
	out=new DataOutputStream(you.getOutputStream());
	while(true)
	{    
		s=in.readUTF();
		m1=Math.random()*100;
		m2=Math.random()*100;
		if(m2>0&&m2<50)
		{
			q=1;
		}
		else
		{
			q=0;
		}
		char a[]=s.toCharArray();
		if((m1>20&&m1<=100)&&((a[0]-'0')==q))
		{
			ta.append("收到:"+s);
			ta.append("\n");
            s2=a[2]+"";
            s3=s3.concat(s2);
            tf.setText(s3);
			out.writeUTF("ack");
		}
		if(m1>=0&&m1<=20)
		{
			ta.append("CRC检测错误!");
			ta.append("\n");
			out.writeUTF("nak");
		}
		else if((a[0]-'0')!=q)
		{
			ta.append("序号不对应丢弃帧");
			ta.append("\n");
			out.writeUTF("nak");
		}
         
	 }
	}catch(IOException e1){}
        
	}
}
public class jie
{
	public static void main(String args[])
	{
		new Se();
	}
}