Java程序设计（9）

十五、网络通信

1.仿照例15.4，编写基于TCP Socket的多客户/服务器通信程序。

//ServerThread.java
import java.io.*;
import java.net.*;
public class ServerThread extends Thread{
	Socket socket=null; 
	int clientnum; //保存本进程的客户序号
	public ServerThread(Socket socket,int num) { 
	     this.socket=socket;
		 clientnum=num+1; 
	}
	public void run() { //线程主体
	    try{
			String line;
			BufferedReader is=new BufferedReader(new InputStreamReader(socket.getInputStream()));
			PrintWriter os=new PrintWriter(socket.getOutputStream());

			BufferedReader sin=new BufferedReader(new InputStreamReader(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(Exception e){
			System.out.println("Error:"+e);
		}
	}
}

//TalkClient.java
import java.io.*;
import java.net.*;
public class TalkClient {
	public static void main(String args[]) {
		try{
			//向本机的4700端口发出客户请求
			Socket socket=new Socket("127.0.0.1",4800);

			BufferedReader sin=new BufferedReader(new InputStreamReader(System.in));
			PrintWriter os=new PrintWriter(socket.getOutputStream());
			BufferedReader is=new BufferedReader(new InputStreamReader(socket.getInputStream()));
			String readline;
			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(Exception e) {
			System.out.println("Error"+e); 
	    }
	}
}

//MultiTalkServer.java
import java.io.*;
import java.net.*;
import ServerThread;
public class MultiTalkServer{
	static int clientnum=0; //记录当前客户的序号
	public static void main(String args[]) throws IOException {
		ServerSocket serverSocket=null;
		try{

			serverSocket=new ServerSocket(4800); 			
		}catch(IOException e) {
			System.out.println("Could not listen on port:4700.");
		
			System.exit(-1); //退出
		}
		while(true){ 
		  new ServerThread(serverSocket.accept(),clientnum).start();
		  clientnum++; 
		}
		serverSocket.close(); 
	}
}

2.仿照例15.5，编写基于UDP数据报的多客户/服务器通信程序。

//QuoteServerThread.java
import java.io.*;
import java.net.*;
import java.util.*;
public class QuoteServerThread extends Thread{  protected DatagramSocket socket=null;
   protected BufferedReader in=null;
   protected boolean moreQuotes=true;
	  public QuoteServerThread() throws IOException {
	    this("QuoteServerThread");
	  }
	  public QuoteServerThread(String name) throws IOException {
		super(name); 
		socket=new DatagramSocket(4445);
		in= new BufferedReader(new InputStreamReader(System.in));
}	
	 public void run() 
	 {
		while(moreQuotes) {
			try{
				byte[] buf=new byte[256]; //创建缓冲区
				DatagramPacket packet=new DatagramPacket(buf,buf.length);
			
				socket.receive(packet); 
				System.out.println(new String(packet.getData())); 
			
				String dString= in.readLine();    
			
				if(dString.equals("bye")){moreQuotes=false;}
				buf=dString.getBytes();
				InetAddress address=packet.getAddress();
				int port=packet.getPort(); 
				packet=new DatagramPacket(buf,buf.length,address,port);
				socket.send(packet);
			}catch(IOException e) { 
			    e.printStackTrace(); 
				moreQuotes=false; 
			}
		 }
		 socket.close(); 
	   }	
}

//QuoteClient .java
import java.io.*;
import java.net.*;
import java.util.*;
public class QuoteClient {
	public static void main(String[] args) throws IOException
		{
		 if(args.length!=1){

		   System.out.println("Usage:java QuoteClient ");
		   return;
		 }
		 DatagramSocket socket=new DatagramSocket();
		 byte[] buf=new byte[256]; 
		 InetAddress address=InetAddress.getByName(args[0]);

		 DatagramPacket packet=new DatagramPacket(buf, buf.length, address, 4445);
		 socket.send(packet); 
		 packet=new DatagramPacket(buf,buf.length);
		 socket.receive(packet); 
		 String received=new String(packet.getData());
		 System.out.println("Quote of the Moment:"+received );		 
		 socket.close(); 
		}
}

public class QuoteServer{
	public static void main(String args[]) throws java.io.IOException
	{
		new QuoteServerThread().start();//启动一个QuoteServerThread线程
	}
}

3.基于TCP Socket的C/S通信与基于UDP数据报的C/S通信有哪些区别？Java分别提供了哪些支持？

TCP协议-Socket

UDP协议-DatagramSocket与DatagramPacket

DatagramSocket：用于发送或接收数据报，是数据报投递服务的一个发送或接收点。

DatagramPacket：用来表示一个数据报