实验3基于UDP的Ping客户机与服务器程序.docx
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实验3基于UDP的Ping客户机与服务器程序.docx
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实验3基于UDP的Ping客户机与服务器程序
自己写一个基于UDP的Ping客户机与服务器程序
这是一个《计算机网络自顶向下方法》中的编程实验。
在本实验中,你将实现一个简单的基于UDP的Ping客户机和服务器。
由这些程序提供的功能类似于现代操作系统中使用的标准Ping程序。
标准的Ping工作时发送因特网控制报文协议(ICMP)ECHO报文,远程机器对发送方返回响应。
该发送方则能够决定它自己和被探测的计算机之间的往返时延。
Java不提供发送和接收ICMP报文的任何功能,所以本实验需要在应用层用标准的UDP套接字和报文实现Ping。
在编译并部署后,客户机的一个运行结果如下:
F:
\EclipseWorkspace\UDPPinger\bin>javaPingClient192.168.173.2407890
FROMSERVER:
PING02010-06-2020:
29:
07
FROMSERVER:
Noreply.
FROMSERVER:
PING22010-06-2020:
29:
09
FROMSERVER:
Noreply.
FROMSERVER:
PING42010-06-2020:
29:
10
FROMSERVER:
Noreply.
FROMSERVER:
PING62010-06-2020:
29:
11
FROMSERVER:
PING72010-06-2020:
29:
11
FROMSERVER:
PING82010-06-2020:
29:
11
FROMSERVER:
PING92010-06-2020:
29:
11
可见第1个、第3个与第5个PING报文没有得到响应。
以下是服务器端对应的运行结果:
D:
\jie.tian\Java\UDPPinger>javaPingServer7890
Receivedfrom+192.168.172.9:
PING02010-06-2020:
29:
07
Replysent.
Receivedfrom+192.168.172.9:
PING12010-06-2020:
29:
08
Replynotsend.
Receivedfrom+192.168.172.9:
PING22010-06-2020:
29:
09
Replysent.
Receivedfrom+192.168.172.9:
PING42010-06-2020:
29:
10
Replysent.
Receivedfrom+192.168.172.9:
PING62010-06-2020:
29:
11
Replysent.
Receivedfrom+192.168.172.9:
PING72010-06-2020:
29:
11
Replysent.
Receivedfrom+192.168.172.9:
PING82010-06-2020:
29:
11
Replysent.
Receivedfrom+192.168.172.9:
PING92010-06-2020:
29:
11
Replysent.
Receivedfrom+192.168.172.9:
PING32010-06-2020:
29:
09
Replysent.
Receivedfrom+192.168.172.9:
PING52010-06-2020:
29:
10
Replysent.
以下分别是服务器程序和客户机程序的Java源代码。
01
importjava.io.*;
02
import.*;
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importjava.util.*;
04
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/**
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*ServertoprocesspingrequestsoverUDP.
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*@author涂鸦
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*
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*/
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publicclassPingServer{
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privatestaticfinaldoubleLOSS_RATE=0.3;
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privatestaticfinalintAVERAGE_DELAY=100; //milliseconds
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publicstaticvoidmain(String[]args)throwsException{
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//Getcommandlineargument.
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if(args.length!
=1){
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System.out.println("Requiredarguments:
port");
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return;
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}
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intport=Integer.parseInt(args[0]);
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//Createrandomnumbergeneratorforuseinsimulatingpacketlossandnetworkdelay.
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Randomrandom=newRandom();
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//CreateadatagramsocketforreceivingandsendingUDPpacketsthroughtheportspecified
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//onthecommandline.
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DatagramSocketsocket=newDatagramSocket(port);
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//Processingloop.
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while(true){
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//CreateadatagrampackettoholdincomingUDPpacket.
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DatagramPacketrequest=newDatagramPacket(newbyte[1024],1024);
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//BlockuntilthehostreceivesaUDPpacket.
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socket.receive(request);
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//Printthereceiveddata.
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printData(request);
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//Decidewhethertoreply,orsimulatepacketloss.
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if(random.nextDouble() 43 System.out.println(" Replynotsend."); 44 continue; 45 } 46 47 //Simulatenetworkdelay. 48 Thread.sleep((int)(random.nextDouble()*2*AVERAGE_DELAY)); 49 50 //Sendreply. 51 InetAddressclientHost=request.getAddress(); 52 intclientPort=request.getPort(); 53 byte[]buf=request.getData(); 54 DatagramPacketreply=newDatagramPacket(buf,buf.length,clientHost,clientPort); 55 socket.send(reply); 56 57 System.out.println(" Replysent."); 58 } 59 } 60 61 /** 62 *Printpingdatatothestandardoutputstream. 63 */ 64 privatestaticvoidprintData(DatagramPacketrequest)throwsException{ 65 //Obtainreferencestothepacket'sarrayofbytes. 66 byte[]buf=request.getData(); 67 68 //Wrapthebytesinabytearrayinputstream,sothatyoucanreadthedataasastream 69 //ofbytes. 70 ByteArrayInputStreambais=newByteArrayInputStream(buf); 71 72 //Wrapthebytearrayoutputstreaminaninputstreamreader, 73 //soyoucanreadthedataasastreamofcharacters. 74 InputStreamReaderisr
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