datagramclient.java

SSD8练习3 传上去大家参考参考 研究研究

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

public class DatagramClient{

	//UDP port to which service is bound
	public static final int SERVICE_PORT = 7;

	//size of the packet
	public static final int SIZE = 1;

	public static void main(String args[]){

		//declare the times that the packets has been resent
		int duplicated=0;

		//declare the total packets that have been received
		int total=0;
		//Get an InetAddress for the specified hostname
		InetAddress addr = null;
		try{

			//resolve the hostname to an InetAddr
			addr = InetAddress.getByName("localhost");
		}
		catch (UnknownHostException ue){

			System.out.println("Unable to resolve host");
			return;
		}
		try{

			//Bind to any free port
			DatagramSocket socket = new DatagramSocket();
			//Set a timeout value of two seconds
			socket.setSoTimeout(2000);
			String message = "a";
			char[] array = message.toCharArray();
			//Get the start time
			Calendar begintime =Calendar.getInstance();
			for(int i=1;i<=1000;i++)
			{
				byte[] sendbuf = new byte[1];
				sendbuf[0]= (byte)array[0];
			
				//Creat a packet to sent to the UDP server
				DatagramPacket sendPacket = new DatagramPacket(
													sendbuf,1,addr,SERVICE_PORT);
				System.out.println("Sending packet to" + "localhost");

				//Send the packet

				socket.send(sendPacket);
				System.out.println("Waiting for packet....");

				//Creat a small packet for receving UDP packets
				byte[] recbuf = new byte[SIZE];
				DatagramPacket receivePacket = new DatagramPacket(recbuf,SIZE);

				//Declare a timeout flag
				boolean timeout = false;

				//catch any InterruptedIOException that is thrown while waiting to recieve a UDP packet

				try{

					socket.receive(receivePacket);
				}
				catch(InterruptedIOException ioe){

					timeout = true;
				}
				if(!timeout){

					System.out.println("packet received!");
					System.out.println("packet " + i + " is revieved");
					total=i;

				}else{

					System.out.println("Packet " + i + "is lost!");
					//send the packet which is lost again
					socket.send(sendPacket);
					while(timeout&(duplicated<=3)){
						
						//calculate the times it has been resend
						duplicated++;					
						System.out.println("Waiting for packet....");

						//Creat a small packet for receving the duplicated UDP packets which is lost
						byte[] dupbuf = new byte[SIZE];
						DatagramPacket dupreceivePacket = new DatagramPacket(dupbuf,SIZE);

						//set the timeout to be false
						timeout = false;

						//catch any InterruptedIOException that is thrown while waiting to recieve a UDP packet

						try{
	
							socket.receive(dupreceivePacket);
						}
						catch(InterruptedIOException ioe){

							timeout = true;
						}
					}
					System.out.println("packet" + i + " has been lost!");
					
				}
				
			}
			//Get the stop time
			Calendar endtime = Calendar.getInstance();
			Date d1 = begintime.getTime();
			Date d2 = endtime.getTime();
			long l1 = d1.getTime();
			long l2 = d2.getTime();
			double differ = Math.abs(l2-l1);
			//calculate the average time
			double average = differ/1000;
			System.out.println(total + " packets have been received.");
			System.out.println("The average time is :" + average+"ms");
			System.out.println("The times packets have been resend is " + duplicated + ".");
		}
		catch (IOException ioe){

			System.out.println("Socket error " + ioe);
		}
	}
}