testudpclientld.java

UDP实现的可靠数据传递的小程序。 考虑了丢包的几种可能性及其处理方法。

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

public class TestUDPClientld
{
	public static void main(String args[]) throws Exception
	{
		Client Try = new Client();
		Try.Execute();
	}
}

class Client
{
	int b,j=1,n=2;//n表示滑动窗口数目为2.j表示读进来的字节存储在data中的位置.b用来保存当前读入的字节.
	byte buf1[] = new byte[1024];//用于发送的缓冲区
	byte buf2[] = new byte[1024];//存储刚发送的数据,丢包时重新发送步buf2
	byte buf3[] = new byte[1024];//用于接受server返回消息.
	char[] data = new char[50];//接受读入数据
	char k1='\u0001';//buf1包中的序号
	char k2='\u0001';//buf2包中的序号
	FileInputStream in = null;
	DatagramSocket ds = null;
	int m;//设定的丢包概率
	int qingkuang;//设置丢包情况：1为两包都丢，2为1包丢，3为2包丢，4为都不丢
	int t1;//包1状态
	int t2;//包2状态
	
	Client() throws Exception
	{
		in = new FileInputStream("C:/Documents and Settings/sc_admin/桌面/test1.txt")	;
		ds = new DatagramSocket(9999);
	}
	
	void Execute() throws Exception
	{

		qingkuang = 3;
		switch(qingkuang)
		{
		case 1:{t1=0;t2=0;break;}
		case 2:{t1=0;t2=1;break;}
		case 3:{t1=1;t2=0;break;}
		case 4:{t1=1;t2=1;break;}
		}
		
		try
		{
			while((b=in.read())!= -1)
			{
				if(j !=41)
				{
					data[j++] = (char)b;
				}
				else
				{
					//把包装好
					SendPacket();
			     	if(n==0)//收消息
			        	Receive();
			       	j=1;//重新将读入字节存储到data中
					data[j++] = (char)b;
					k1++;
				}
			 }//while
			 //最后一个包
			 FinalPacket();
			 in.close();
		}
		catch(FileNotFoundException e2)
		{
			System.out.println("File Not Found");
			System.exit(-1);
		}
		catch(IOException e1)
		{
			System.out.println("File Copy error");
			System.exit(-1);
		}
	}//Execcute
	
	void SendPacket() throws Exception
	{//将封装好的包发给Server
		//int probability;//要发送包的丢包概率
		//probability=(int)(Math.random()*100);
		data[0] = k1;//加入序号.	
		String str = new String(data);
		buf1 = str.getBytes();		
		DatagramPacket dp1 = new DatagramPacket(buf1, buf1.length, new InetSocketAddress("127.0.0.1", 5678));
		if(n!=0)
		{//probability>=m
			if(t1==1)
			{
				System.out.println((int)k1+"传递包1");
				ds.send(dp1);
			}
			else
			{
				System.out.println((int)k1+"不传递包1");
			}
			
			if(n==2)
			{
				Save(buf2,buf1);
				k2=k1;
			}
			n--;
		}
	}//SendPacket
	
	void Save(byte[] a,byte[] b)
	{
		for(int j = 0;j<50;j++)
			a[j]=b[j];	
	}//Save
	
	void Receive() throws Exception
	{
		
				
		DatagramPacket dp2 = new DatagramPacket(buf3,buf3.length);
	
		while(true)
		{
			
		//	System.out.println("dengdai");
			ds.setSoTimeout(1150);
		 	try
			{//	System.out.println(buf3[0]);
	 		//	System.out.println((int)k1);
				ds.receive(dp2);
			}
			catch(SocketTimeoutException ex)
			{}
		//	System.out.println("yiguo");
			if(buf3[0]==(int)k2)
		 	{
		 		if(k2=='\u0000')
		 			System.out.println("最后一包已经到达");
		 		else
		 			System.out.println("包"+(int)k2+"已经到达");
		 		if(k1==k2)
		 			break;
		 		k2++;
		 		ds.setSoTimeout(5);
			 	try
				{
					ds.receive(dp2);
				}
				catch(SocketTimeoutException ex)
				{}
		 	
		 		if(buf3[0]==(int)k1)
		 		{
		 		
		 			System.out.println("包"+(int)k2+"已经到达");
		 			break;
		 		}
		 		else
		 		{
		 			DatagramPacket dp4 = new DatagramPacket(buf1, buf1.length, new InetSocketAddress("127.0.0.1", 5678));
					ds.send(dp4);
					System.out.println("重传了"+(int)k2);	
					if(k1=='\u0000')
						k2=k1;
		 		}
		 		
		 	}
			else
			{
				DatagramPacket dp3 = new DatagramPacket(buf2, buf2.length, new InetSocketAddress("127.0.0.1", 5678));
				System.out.println("重传了"+(int)k2);
				ds.send(dp3);
				DatagramPacket dp4 = new DatagramPacket(buf1, buf1.length, new InetSocketAddress("127.0.0.1", 5678));
				System.out.println("重传了"+(int)(k2+1));
				ds.send(dp4);
			}
		}
		n=2;
	}//Receive
	
	void FinalPacket() throws Exception
	{
		j=j-1;//j-1后才表示的是data中最后一个元素的下标
		if(j==40)
		{
			SendFinal();
			if(n==1)//最后一包为偶数包
				Receive();
				
			else//最后一包为奇数包
				FinalReceive();
		}//1if
		else
		{
			j++;
			for(;j<=41;j++)
				data[j]='\u0000';
			SendFinal();
			if(n==1)//最后一包为偶数包	
				Receive();
			else//最后一包为奇数包
				FinalReceive();
		}//1else
	}//FinalPacket
	
	void SendFinal() throws Exception
	{
		//int probability;
		//probability=(int)(Math.random()*100);
		data[42]=k1;
		k1='\u0000';
		data[0] = k1;
		String str = new String(data);
		buf1 = str.getBytes();
		DatagramPacket dp1 = new DatagramPacket(buf1, buf1.length, new InetSocketAddress("127.0.0.1", 5678));
	//	System.out.println("m is"+m+"k1 is"+(int)(k2+1));
		if(t2==1)
		{
			System.out.println((int)(k2+1)+"传递包2");
			ds.send(dp1);
		}
		else
		{
			System.out.println((int)(k2+1)+"不传递包2");
		}
	}//SendFinal
	
	void FinalReceive() throws Exception
	{
		while(true)
		{
			DatagramPacket dp2 = new DatagramPacket(buf3,buf3.length);
		//	System.out.println("shouZQbao");
			ds.setSoTimeout(5);
		 	try
			{//	System.out.println(buf3[0]);
	 		//	System.out.println((int)k1);
				ds.receive(dp2);
			}
			catch(SocketTimeoutException ex)
			{}
			if(buf3[0]==(int)k1)
		 	{
		 		k2++;
		 		System.out.println("3包"+(int)k2+"已经到达");		 						 		
		 		break;
			}
			else
			{
				DatagramPacket dp3 = new DatagramPacket(buf1, buf1.length, new InetSocketAddress("127.0.0.1", 5678));
				ds.send(dp3);
			}
		}
				
	}//FinalReceive
	
	
}