Java程序开发教学课件13-网络通信

Java程序开发网络通信重庆大学计算机学院主要内容

协议，主机，端口

URLConnection

Socket通信

多客户机制

扩展：ftp，http等下载和通信程序网络基础知识

IP地址如：,0

主机名(hostname)如：

端口号(portnumber)如:80，21，23，25

服务类型(service)http,telnet,ftp,smtp两类传输协议

TCP(TransportControlProtocol)面向连接的能够提供可靠的流式数据传输的协议。类似于打电话的过程。URL,URLConnection,Socket,ServerSocket等类都使用TCP协议进行网络通讯。

UDP(UserDatagramProtocol)非面向连接的提供不可靠的数据包式的数据传输的协议。类似于从邮局发送信件的过程。DatagramPacket,DatagramSocket,MulticastSocket等类使用UDP协议进行网络通讯。URL类

URL(UniformResourceLocator)一致资源定位器的简称，它表示Internet上某一资源的地址。

URL的组成protocol:resourceName协议名指明获取资源所使用的传输协议，如http、ftp、gopher、file等，资源名则应该是资源的完整地址，包括主机名、端口号、文件名或文件内部的一个引用。URL例子

/

/home/welcome.html

:80/Gamelan/network.html#BOTTOM构造URL对象publicURL(Stringspec)URLurlBase=newURL(“/”);publicURL(URLcontext,Stringspec)URLibm=newURL(“/pages/");URLibmgame=new(ibm,"game.html");例外处理try{URLmyURL=newURL(...)}catch(MalformedURLExceptione){.//exceptionhandlercodehere.....}获取URL对象属性

publicStringgetProtocol()

publicStringgetHost()

publicStringgetPort()

publicStringgetFile()

publicStringgetRef()类InetAddress

InetAddress类是IP地址封装类

InetAddressgetByName（Stringhostname）

InetAddressgetByAddress(byte[]addr)

StringgetHostAddress()

StringgetHostName()获得有关IP地址的各种属性通过URL读取WWW信息publicclassURLReader{publicstaticvoidmain(String[]args)throwsException{URLcqu=newURL(“/");BufferedReaderin=newBufferedReader(newInputStreamReader(cqu.openStream()));StringinputLine;while((inputLine=in.readLine())!=null)System.out.println(inputLine);in.close();}}使用URLConnection读写WWW资源try{URLcqu=newURL("/");URLConnectionntc=cqu.openConnection();}catch(MalformedURLExceptione){//newURL()failed...}catch(IOExceptione){//openConnection()failed...}

得到URLConnection对象之后，可以用如下方法得到相应的输入/输出流：

getInputStream()

getOutputStream()之后就可以读写输入/输出流，完成数据的读写。socket通讯

网络上的两个程序通过一个双向的通讯连接实现数据的交换，这个双向链路的一端称为一个socket。

socket通常用来实现客户方和服务方的连接。Client-serverandServiceSocketCommunicationSocket编程模型ClientServerServerSocketwaitrequestnewSocketnewSocketacceptsendRead/WriteDatareceiveRead/WriteDatareceivesendcloseCloseSocketCloseSocketclose创建Socket和ServerSocket

Socket(InetAddressaddress,intport);

Socket(InetAddressaddress,intport,booleanstream);

Socket(Stringhost,intport);

Socket(Stringhost,intport,booleanstream);

ServerSocket(intport);

ServerSocket(intport,intcount);客户端Socket的建立try{Socketsocket=newSocket(”",2000);}catch(IOExceptione){System.out.println("Error:"+e);}服务器端Socket的建立ServerSocketserver=null;try{server=newServerSocket(2000);}catch(IOExceptione){System.out.println("cannotlistento:"+e);}Socketsocket=null;try{socket=server.accept();}catch(IOExceptione){System.out.println("Error:"+e);}打开输入/输出流PrintStreamos=newPrintStream(newBufferedOutputStream(socket.getOutputStream()));DataInputStreamis=newDataInputStream(socket.getInputStream());PrintWriterout=newPrintWriter(socket.getOutputStream(),true);BufferedReaderin=newBufferedReader(newInputStreamReader(socket.getInputStream()));关闭socket

os.close();

is.close();

socket.close();

注意关闭的顺序例客户端程序importjava.io.*;.*;publicclassTalkClient{publicstaticvoidmain(Stringargs[]){try{Socketsocket=newSocket(“”,4700);BufferedReadersin=newBufferedReader(newInputStreamReader(System.in));PrintWriteros=newPrintWriter(socket.getOutputStream());BufferedReaderis=newBufferedReader(newInputStreamReader(socket.getInputStream()));Stringreadline;readline=sin.readLine();while(!readline.equals(“bye”)){os.println(readline);os.flush();System.out.println(“Client:”+readline);System.out.println(“Server:”+is.readLine());readline=sin.readLine();}os.close();is.close();socket.close();}catch(Exceptione){System.out.println(“Error”+e);}}}服务器端程序:importjava.io.*;.*;publicclassTalkServer{publicstaticvoidmain(Stringargs[]){try{ServerSocketserver=null;try{server=newServerSocket(4700);}catch(Exceptione){System.out.println(“cannotlistento:”+e);}Socketsocket=null;try{socket=server.accept();}catch(Exceptione){System.out.println(“Error.”+e);}Stringreadline;BufferedReaderis=newBufferedReader(newInputStreamReader(socket.getInputStream()));PrintWriteros=newPrintWriter(socket.getOutputStream());BufferedReadersin=newBufferedReader(newInputStreamReader(System.in));System.out.println(“Client:”+is.readLine());readline=sin.readLine();while(!readline.equals(“bye”)){os.println(readline);os.flush();System.out.println(“Server:”+readline);System.out.println(“Client:”+is.readLine());readline=sin.readLine();}os.close();is.close();socket.close();server.close();}catch(Exceptione){System.out.println(“Error:”+e);}}}运行结果Server:hello!Client:hello!Server:howareyou?Client:Iamfine,thankyou!…Client:bye.Server:bye.多客户机制SocketThreadAClientASocketThreadBServerSocketClientBThreadCSocketClientC服务器端程序:MultiTalkServer.javatry{serverSocket=newServerSocket(4700);}catch(IOExceptione){System.out.println("Couldnotlisten");System.exit(-1);}while(listening){newServerThread(serverSocket.accept(),clientnum).start();clientnum++;}程序ServerThread.javaimportjava.io.*;.*;publicclassServerThreadextendsThread{Socketsocket=null;clientnum;publicServerThread(Socketsocket,intnum){this.socket=socket;clientnum=num+1;}publicvoidrun(){try{Stringline;BufferedReaderis=newBufferedReader(newInputStreamReader(socket.getInputStream()));PrintWriteros=newPrintWriter(socket.getOutputStream());BufferedReadersin=newBufferedReader(newInputStreamReader(System.in));System.out.println(“Client”+clientnum+”:”+is.readLine());line=sin.readLine();while(!line.equals(“bye”)){os.println(line);os.flush();System.out.println(“Server:”+line);System.out.println(“Client:”+clientnum+“:”is.readLine());line=sin.readLine();}os.close();is.close();socket.close();}catch(Exceptione){System.out.println(“Error:”+e);}}}server.close();}catch(Exceptione){System.out.println(“Error:”+e);}}}数据报通信

TCP(TransportControlProtocol)面向连接的能够提供可靠的流式数据传输的协议。类似于打电话的过程。URL,URLConnection,Socket,ServerSocket等类都使用TCP协议进行网络通讯。

UDP(UserDatagramProtocol)非面向连接的提供不可靠的数据包式的数据传输的协议。类似于从邮局发送信件的过程。DatagramPacket,DatagramSocket,MulticastSocket等类使用UDP协议进行网络通讯。比较通信方协议是否需要连可靠性数据量应用式接无连接，每不可靠，64KB之数据会丢失数据报UDP个报包括源地址和目标地址时间服务，ping程序通信内可靠，http服务，流式通TCP需要连接大量数Telnet服务，信数据不会丢失据Ftp服务数据报通信

TCP有建立时间

UDP传输有大小限制:64K以内

TCP的应用:Telnet,ftp

UDP的应用:ping数据报通信

DatagramSocket()

DatagramSocket(intport)

DatagramPacket(byteibuf[],intilength)

DatagramPacket(byteibuf[],intilength,InetAddressiaddr,intiport);数据报通信

收数据报:DatagramPacketpacket=newDatagramPacket(buf,256);socket.receive(packet);

发数据报DatagramPacketpacket=newDatagramPacket(buf,buf.length,address,port);socket.send(packet);客户方程序QuoteClient.javaimportjava.io.*;.*;importjava.util.*;publicclassQuoteClient{publicstaticvoidmain(String[]args)throwsIOException{if(args.length!=1){System.out.println(“Usage:javaQuoteClient<hostname>”);return;}DatagramSocketsocket=newDatagramSocklet();//sendrequestByte[]buf=newbyte[256];InetAddressaddress=InetAddress.getByName(args[0]);DatagramPacketpacket=newDatagramPacket(buf,buf.length,address,4445);socket.send(packet);//getresponsepacket=newDatagramPacket(buf,buf.length);socket.receive(packet);//displayresponseStringreceived=newString(packet.getData());System.out.println(“QuoteoftheMoment:”+received);socket.close();服务器方程序:QuoteServer.javapublicclassQuoteServer{publicstaticvoidmain(Stringargs[])throwsjava.io.IOException{newQuoteServerThread().start();}}程序QuoteServerThread.javaimportjava.io.*;.*;importjava.util.*;publicclassQuoteServerThreadextendsThread{protectedDatagramSocketsocket=null;protectedBufferedReaderin=null;protectedbooleanmoreQuotes=true;publicQuoteServerThread()throwsIOException{this(“QuoteServerThread”);}publicQuoteServerThread(S)throwsIOException{super(name);socket=newDatagramSocket(4445);try{in=newBufferedReader(newFileReader(“one-liners.txt”));}catch(FileNotFoundExceptione){System.err.println(“Couldnotopenquotefile.Servingtimeinstead.”);}}publicvoidrun(){while(moreQuotes){try{byte[]buf=newbyte[256];DatagramPacketpacket=newDatagramPacket(buf,buf.length);socket.receive(packet);StringdString=null;if(in==null)dString=newDate().toString();elsedString=getNextQuote();buf=dString.getByte();//sendtheresponsetotheclientat”address”and//“port”InetAddressaddress=packet.getAddress();intport=packet.getPort();packet=newDatagramPacket(buf,buf.length,address,port);socket.send(packet);}catch(IOExceptione){e.printStackTrace();moreQuotes=false;}}socket.close();}protectedStringgetNextQuotes(){StringreturnValue=null;try{if((returnValue=in.readLine())==null){in.close();moreQuotes=false;returnValue=“Nomorequotes.Goodbye.”;}}catch(IOEceptione){returnValue=“IOExceptionoccurredinserver”;}returnreturnValue;}使用数据报进行广播通信

DatagramSocket只运行数据报发往一个目的地址

MulticastSocket将数据报以广播方式发送到该端口的所有客户.

MulticastSocket用在客户端,监听服务器广播来的数据客户方程序:MulticastClient.javaimportjava.io.*;.*;importjava.util.*;publicclassMulticastClient{publicstaticvoidmain(Stringargs[])throwsIOException{MulticastSocketsocket=newMulticastSocket(4446);InetAddressaddress=InetAddress.getByName(“”);socket.joinGroup(address);DatagramPacketpacket;//getafewquotesfor(inti=0;i<5;i++){byte[]buf=newbyte[256];packet=newDatagramPacket(buf,buf.length);socket.receive(packet);Stringreceived=newS