一个JAVA模拟实现的停等协议

计算机网络——自顶向下方法，第三章编程作业，实现可靠传输协议，这里写了一个模拟停等协议的程序，没有写GBN的。

分组丢失和ACK丢失都是通过随机数进行模拟的。

接收方程序：

import java.io.*;
import java.net.*;

public class Receiver extends Thread{
	 private boolean OutServer = false; 
	 private static ServerSocket server ; 
	 private static  int ServerPort = 9878; 
	
	public static void main(String[] args) {
		(new Receiver()).start();
		}
	
	public Receiver() 
	  { 
	    try 
	    { 
	      server = new ServerSocket(ServerPort); 
	    } 
	    catch(java.io.IOException e) 
	    { 
	      System.out.println("Socket啟動有問題 !" ); 
	      System.out.println("IOException :" + e.toString()); 
	    } 
	  } 	
	
	public void run() 
	  { 
	    Socket socket ; 
	    ObjectInputStream in ; 
	 
	    System.out.println("伺服器已啟動 !"  ); 
	    while(!OutServer) 
	    { 
	      socket = null; 
	      try 
	      { 
	        synchronized(server) 
	        { 
	          socket = server.accept(); 
	        } 
	        //System.out.println("取得連線 : InetAddress = " + socket.getInetAddress()); 
	        socket.setSoTimeout(15000); 
	 
	 
	        in = new ObjectInputStream(socket.getInputStream()); 
	 
	        Msg data = (Msg)in.readObject(); 
	        System.out.println("发送端正在发送的内容"+data.getN_msg()+"  状态："+data.getInfo()); 
	        if(data.getInfo().equals("losePackage"))
	        {
	        	System.out.println("分组丢失");
	        	DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
	        	dos.writeBytes("resend1"+'\n');
	        	dos.close();
	        }
	        else if(data.getInfo().equals("loseAck"))
	        {
	        	System.out.println("ACK丢失");
	        	DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
	        	dos.writeBytes("resend2"+'\n');
	        	dos.close();
	        }
	        else
	        {
	        	System.out.println("接收分组 "+data.getN_msg()+"   发送ACK "+data.getN_msg());
	        	DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
	        	dos.writeBytes("ok"+'\n');
	        	dos.close();
	        }
	        System.out.println();
	        
	        
	        in.close(); 
	        in = null ; 
	        socket.close();
	 
	      } 
	      catch(java.io.IOException e) 
	      { 
	    	  System.out.println("Socket連線有問題111 !" ); 
	    	  System.out.println("IOException :" + e.toString()); 
	      } 
	      catch(java.lang.ClassNotFoundException e) 
	      { 
	    	  System.out.println("ClassNotFoundException :" + e.toString()); 
	      } 
	    } 
	  } 
	
}

 发送端程序

import java.io.*;
import java.net.*;

public class Sender extends Thread{
	private String address = "127.0.0.1"; 
	 private int port = 9878; 
	 
	 public Sender() {
		 Socket client = null ;
		 for(int i=0;i<10; i++)
		 {
			 client = new Socket() ;
			 Msg data = new Msg(i%2); 
			 InetSocketAddress isa = new InetSocketAddress(this.address,this.port); 
	        try 
	        { 
	        	client.connect(isa,10000); 
	        	ObjectOutputStream out = new ObjectOutputStream(client.getOutputStream()); 
	        	
	        	out.writeObject(data); 
	        	System.out.println("发送分组 "+data.getN_msg());
	        	
	        	
	        	BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
		        String str = br.readLine();
		        if(str.equals("resend1"))
		        {
		        	System.out.println("分组丢失，重发");
		        	i--;
	        		out.flush(); 
		        	out.close(); 
		        	out = null ; 
		        	data = null ;
		        	client.close();
					client = null ; 
	        		continue;
		        }
		        else if(str.equals("resend2"))
		        {
		        	System.out.println("ACK丢失，重发");
		        	i--;
	        		out.flush(); 
		        	out.close(); 
		        	out = null ; 
		        	data = null ;
		        	client.close();
					client = null ; 
	        		continue;
		        }
		        else System.out.println("\n"+"接收ACK"+data.getN_msg()+"      发送分组"+(data.getN_msg()+1)%2);
	        	
	        	
	        	out.flush(); 
	        	out.close(); 
	        	out = null ; 
	        	data = null ;
	        	client.close();
				client = null ; 
	 
	        } 
	        catch(java.io.IOException e) 
	        { 
	          System.out.println("Socket連線有問題 222!" ); 
	          System.out.println("IOException :" + e.toString()); 
	        } 
	        try {
				this.sleep(8000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		 }
	}
	 
	public static void main(String[] args) {
		new Sender();
	}

}

 信息类Msg：

import java.io.Serializable;
import java.util.*;

public class Msg implements Serializable{
	private int n_msg;
	private String info;
	private Random random; 
	private int rdNum;
	
	public Msg(int n_msg) {
		this.n_msg = n_msg;
		MsgState();
	}
	
	public void MsgState(){//用于模拟分组丢失，ACK丢失等情况
		random = new Random();
		rdNum = Math.abs(random.nextInt())%100;
		if (rdNum<20) info = "losePackage";
		else if(rdNum>80) info ="loseAck";
		else info ="noError";
 		
	}
	
		
	public int getN_msg() {
		return n_msg;
	}
	public void setN_msg(int n_msg) {
		this.n_msg = n_msg;
	}

	public String getInfo() {
		return info;
	}

	public void setInfo(String info) {
		this.info = info;
	}
}