第13章课后答案

一、问答题

1．一个URL对象通常包含最基本的三部分信息：协议、地址、资源。

2．URL对象调用InputStreamopenStream() 方法可以返回一个输入流，该输入流指向URL对象所包含的资源。通过该输入流可以将服务器上的资源信息读入到客户端。

3．客户端的套接字和服务器端的套接字通过输入、输出流互相连接后进行通信。

4．使用方法accept()，accept()会返回一个和客户端Socket对象相连接的Socket对象。accept方法会堵塞线程的继续执行，直到接收到客户的呼叫。。

5．域名/IP。

四、编程题

1.  （1）客户端

import java.net.*;

import java.io.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Client

{  public static void main(String args[])

   {  newComputerClient();

   }

}

class ComputerClient extendsFrame implements Runnable,ActionListener

{  Button connection,send;

   TextField inputText,showResult;

   Socket socket=null;

   DataInputStream in=null;

   DataOutputStream out=null;

   Thread thread;

   ComputerClient()

   { socket=new Socket();

      setLayout(new FlowLayout());

      Box box=Box.createVerticalBox();

      connection=new Button("连接服务器");

      send=new Button("发送");

      send.setEnabled(false);

      inputText=new TextField(12);

      showResult=new TextField(12);

      box.add(connection);

      box.add(new Label("输入三角形三边的长度,用逗号或空格分隔:"));

      box.add(inputText);

      box.add(send);

      box.add(new Label("收到的结果："));

      box.add(showResult);

      connection.addActionListener(this);

      send.addActionListener(this);

      thread=new Thread(this);

      add(box);

      setBounds(10,30,300,400);

      setVisible(true);

      validate();

      addWindowListener(new WindowAdapter()

                   {  public void windowClosing(WindowEvent e)

                            {  System.exit(0);

                            }

                   });

   }

   public void actionPerformed(ActionEvent e)

   { if(e.getSource()==connection)

      { try  //请求和服务器建立套接字连接：

         { if(socket.isConnected())

              {}

           else

              { InetAddress address=InetAddress.getByName("127.0.0.1");

                InetSocketAddresssocketAddress=new InetSocketAddress(address,4331);

                socket.connect(socketAddress);

                in =newDataInputStream(socket.getInputStream());

                out = newDataOutputStream(socket.getOutputStream());

                send.setEnabled(true);

                thread.start();

               }

         }

         catch (IOException ee){}

      }

     if(e.getSource()==send)

      { String s=inputText.getText();

         if(s!=null)

           { try { out.writeUTF(s);

                  }

              catch(IOException e1){}

           }              

      }

   }

   public void run()

   { String s=null;

      while(true)

       {   try{  s=in.readUTF();

                  showResult.setText(s);

               }

           catch(IOException e)

               { showResult.setText("与服务器已断开");

                      break;

               }  

       }

  }

}

（2）服务器端

import java.io.*;

import java.net.*;

import java.util.*;

public class Server

{  public static void main(String args[])

   { ServerSocket server=null;

      Server_thread thread;

      Socket you=null;

      while(true)

       { try{  server=newServerSocket(4331);

             }

          catch(IOException e1)

                { System.out.println("正在监听"); //ServerSocket对象不能重复创建

           }

          try{ System.out.println(" 等待客户呼叫");

                you=server.accept();

                System.out.println("客户的地址:"+you.getInetAddress());

             }

         catch (IOException e)

             { System.out.println("正在等待客户");

             }

         if(you!=null)

            {  new Server_thread(you).start(); //为每个客户启动一个专门的线程 

          }

       }

   }

}

class Server_thread extendsThread

{  Socket socket;

   DataOutputStream out=null;

   DataInputStream  in=null;

   String s=null;

   boolean quesion=false;

   Server_thread(Socket t)

   { socket=t;

      try { out=new DataOutputStream(socket.getOutputStream());

             in=newDataInputStream(socket.getInputStream());

          }

      catch (IOException e)

          {}

   } 

   public void run()       

   { while(true)

      { double a[]=new double[3] ;

         int i=0;

         try{ s=in.readUTF();//堵塞状态，除非读取到信息

               quesion=false;

               StringTokenizer fenxi=newStringTokenizer(s," ,");

                 while(fenxi.hasMoreTokens())

                   {  String temp=fenxi.nextToken();

                      try{  a[i]=Double.valueOf(temp).doubleValue();i++;

                         }

                     catch(NumberFormatException e)

                         {  out.writeUTF("请输入数字字符");

                            quesion=true;

                         }

                   }

                if(quesion==false)

                {  double p=(a[0]+a[1]+a[2])/2.0;

                   out.writeUTF(""+Math.sqrt(p*(p-a[0])*(p-a[1])*(p-a[2])));

                }

            }

         catch (IOException e)

            { System.out.println("客户离开");

               return;

            }

      }

   }

}

2.   客户端Client.java

import java.net.*;

import java.io.*;

import java.awt.*;

importjava.awt.event.*;

importjavax.swing.*;

public classClient

{  public static void main(String args[])

   {  newChatClient();

   }

}

class ChatClientextends Frame implements Runnable,ActionListener

{  Button connection,send;

   TextField inputName,inputContent;

   TextArea chatResult;

   Socket socket=null;

   DataInputStream in=null;

   DataOutputStream out=null;

   Thread thread;

   String name="";

   public ChatClient ()

   { socket=new Socket();

      Box box1=Box.createHorizontalBox();

      connection=new Button("连接服务器");

      send=new Button("发送");

      send.setEnabled(false);

      inputName=new TextField(6);

      inputContent=new TextField(22);

      chatResult=new TextArea();

      box1.add(new Label("输入妮称:"));

      box1.add(inputName);

      box1.add(connection);

      Box box2=Box.createHorizontalBox();

      box2.add(new Label("输入聊天内容:"));

      box2.add(inputContent);

      box2.add(send);

      connection.addActionListener(this);

      send.addActionListener(this);

      thread=new Thread(this);

      add(box1,BorderLayout.NORTH);

      add(box2,BorderLayout.SOUTH);

      add(chatResult,BorderLayout.CENTER);

      setBounds(10,30,400,280);

      setVisible(true);

      validate();

      addWindowListener(new WindowAdapter()

                   {  public void windowClosing(WindowEvent e)

                            {  System.exit(0);

                            }

                   });

   }

   public void actionPerformed(ActionEvent e)

   { if(e.getSource()==connection)

      {  try 

         { if(socket.isConnected())

              {}

           else

              { InetAddress address=InetAddress.getByName("127.0.0.1");

                InetSocketAddresssocketAddress=new InetSocketAddress(address,666);

                socket.connect(socketAddress);

                in =newDataInputStream(socket.getInputStream());

                out = newDataOutputStream(socket.getOutputStream());

                name=inputName.getText();

                out.writeUTF("姓名:"+name);

                send.setEnabled(true);

                if(!(thread.isAlive()))

                   thread=new Thread(this);

                thread.start();

               }

         }

         catch (IOException ee){}

      }

     if(e.getSource()==send)

      { String s=inputContent.getText();

         if(s!=null)

           { try { out.writeUTF("聊天内容:"+name+":"+s);

                  }

              catch(IOException e1){}

           }              

      }

   }

   public void run()

   { String s=null;

      while(true)

       {   try{  s=in.readUTF();

                 chatResult.append("\n"+s);

               }

           catch(IOException e)

               {  chatResult.setText("与服务器已断开");

                  try { socket.close();

                      }

                  catch(Exception exp) {}

                  break;

               }  

       }

  }

}

服务器端ChatServer.java

import java.io.*;

import java.net.*;

importjava.util.*;

public classChatServer

{  public static void main(String args[])

    { ServerSocket server=null;

      Socket you=null;

      Hashtable peopleList;      

      peopleList=new Hashtable();

      while(true)

            { try  { server=new ServerSocket(666);

                  }

             catch(IOException e1)

                  {  System.out.println("正在监听");

                  }

             try  { you=server.accept();                

                     InetAddressaddress=you.getInetAddress();

                     System.out.println("客户的IP:"+address);

                  }

             catch (IOException e) {}

             if(you!=null)

                  {  Server_thread peopleThread=newServer_thread(you,peopleList);

                     peopleThread.start();              

                  }

             else {  continue;

                  }

           }

  }

}

classServer_thread extends Thread

{  String name=null;     

   Socket socket=null;

   File file=null;

   DataOutputStream out=null;

   DataInputStream  in=null;

   Hashtable peopleList=null;

   Server_thread(Socket t,Hashtable list)

       { peopleList=list;

         socket=t;

         try { in=new DataInputStream(socket.getInputStream());

                out=newDataOutputStream(socket.getOutputStream());

             }

         catch (IOException e) {}

        } 

  public void run()       

  {  while(true)

      { String s=null;  

        try{

            s=in.readUTF();                      

            if(s.startsWith("姓名:"))            

              { name=s;

                boolean boo=peopleList.containsKey(name);

                if(boo==false)

                  {peopleList.put(name,this);         

                  }

                else

                  { out.writeUTF("请换妮称:");

                    socket.close();

                    break;

                  }

              }

            else if(s.startsWith("聊天内容"))

              { String message=s.substring(s.indexOf(":")+1);

                 EnumerationchatPersonList=peopleList.elements();   

                while(chatPersonList.hasMoreElements())

                 {    ((Server_thread)chatPersonList.nextElement()).out.writeUTF("聊天内容:"+

message);

                 } 

              }

           }

        catch(IOException ee)  

           {    Enumeration chatPersonList=peopleList.elements();   

                while(chatPersonList.hasMoreElements())            

                   { try

                     {  Server_thread th=(Server_thread)chatPersonList.nextElement();

                       if(th!=this&&th.isAlive())

                         { th.out.writeUTF("客户离线:"+name);

                         }

                     }

                     catch(IOException eee){}

                   }

                 peopleList.remove(name);

                 try { socket.close();

                    }                   

                 catch(IOException eee){}

                 System.out.println(name+"客户离开了");

                 break;     

           }            

     }

  }

}

3．BroadCastWord.java

import java.io.*;

import java.net.*;

import java.awt.*;

importjava.awt.event.*;

importjavax.swing.Timer;

public classBroadCastWord extends Frame implements ActionListener

{  int port;

   InetAddress group=null;

   MulticastSocket socket=null;

   Timer time=null;

   FileDialog open=null;

   Button select,开始广播,停止广播;

   File file=null;

   String FileDir=null,fileName=null;

   FileReader in=null;

   BufferedReader bufferIn=null;

   int token=0;

   TextArea 显示正在播放内容,显示已播放的内容;

  public BroadCastWord()

  { super("单词广播系统");

   select=new Button("选择要广播的文件");

   开始广播=new Button("开始广播");

   停止广播=new Button("停止广播");

   select.addActionListener(this);

   开始广播.addActionListener(this);

   停止广播.addActionListener(this);

   time=new Timer(2000,this);

   open=new FileDialog(this,"选择要广播的文件",FileDialog.LOAD); 

   显示正在播放内容=new TextArea(10,10);

   显示正在播放内容.setForeground(Color.blue);

   显示已播放的内容=new TextArea(10,10);

   Panel north=new Panel();

   north.add(select);

   north.add(开始广播);

   north.add(停止广播);

   add(north,BorderLayout.NORTH);

   Panel center=new Panel();

   center.setLayout(new GridLayout(1,2));

   center.add(显示正在播放内容);

   center.add(显示已播放的内容);

   add(center,BorderLayout.CENTER);

   validate();

   try

      { port=5000;                                  

      group=InetAddress.getByName("239.255.0.0"); 

       socket=new MulticastSocket(port);           

       socket.setTimeToLive(1);                    

       socket.joinGroup(group);                    

      }

  catch(Exception e)

       { System.out.println("Error:"+ e);         

       }

  setBounds(100,50,360,380);  

  setVisible(true);

  addWindowListener(new WindowAdapter()

                     { public voidwindowClosing(WindowEvent e)

                       { System.exit(0);

                           }

                         });

 }

 public void actionPerformed(ActionEvent e)

 { if(e.getSource()==select)

     {显示已播放的内容.setText(null);

      open.setVisible(true);

      fileName=open.getFile();

      FileDir=open.getDirectory();

      if(fileName!=null)

       { time.stop();      

         file=new File(FileDir,fileName);

         try

            {  file=new File(FileDir,fileName);

               in=new FileReader(file);                     

               bufferIn=new BufferedReader(in);

            }

         catch(IOException ee) { }

       }

     }

   else if(e.getSource()==开始广播)

     {  time.start();

     }

   else if(e.getSource()==time)

     { String s=null;

        try {  if(token==-1)

                 { file=newFile(FileDir,fileName);

                   in=newFileReader(file);                      

                   bufferIn=newBufferedReader(in);

                 }

              s=bufferIn.readLine();

              if(s!=null)

                { token=0;

                  显示正在播放内容.setText("正在广播的内容:\n"+s);

                  显示已播放的内容.append(s+"\n");

                  DatagramPacketpacket=null;    

                  byte data[]=s.getBytes();

                  packet=newDatagramPacket(data,data.length,group,port);

                  socket.send(packet);    

                }

              else

                {  token=-1;

                }

            }

        catch(IOException ee) { }

     }

   else if(e.getSource()==停止广播)

     { time.stop();

     }

 }

public static voidmain(String[] args)

   { BroadCastWord broad=new BroadCastWord();

   }

}

Receive.java

import java.net.*;

import java.awt.*;

importjava.awt.event.*;

public classReceive extends Frame implements Runnable,ActionListener

{  int port;                                       

  InetAddress group=null;                          

  MulticastSocket socket=null;                    

  Button 开始接收,停止接收;  

  TextArea 显示正在接收内容,显示已接收的内容; 

  Thread thread;                                  

  boolean 停止=false;

  public Receive()

   {  super("定时接收信息");

     thread=new Thread(this);

     开始接收=new Button("开始接收");

     停止接收=new Button("停止接收");

     停止接收.addActionListener(this);

     开始接收.addActionListener(this);

     显示正在接收内容=new TextArea(10,10);

     显示正在接收内容.setForeground(Color.blue);

     显示已接收的内容=new TextArea(10,10);

    Panel north=new Panel();

     north.add(开始接收);

     north.add(停止接收);

     add(north,BorderLayout.NORTH);

     Panel center=new Panel();

     center.setLayout(new GridLayout(1,2));

     center.add(显示正在接收内容);

     center.add(显示已接收的内容);

     add(center,BorderLayout.CENTER);

     validate();

     port=5000;                                      

     try{group=InetAddress.getByName("239.255.0.0"); 

         socket=new MulticastSocket(port);           

         socket.joinGroup(group);          

       }

    catch(Exception e) { }

    setBounds(100,50,360,380);  

    setVisible(true);

    addWindowListener(new WindowAdapter()

                     { public voidwindowClosing(WindowEvent e)

                       { System.exit(0);

                           }

                         });

                           

   }

  public void actionPerformed(ActionEvent e)

   { if(e.getSource()==开始接收)

      { 开始接收.setBackground(Color.blue);

        停止接收.setBackground(Color.gray);

        if(!(thread.isAlive()))

           { thread=new Thread(this);

           }

        try {  thread.start();

             停止=false;       

           }

        catch(Exception ee) { }

      }

    if(e.getSource()==停止接收)

      { 开始接收.setBackground(Color.gray);

        停止接收.setBackground(Color.blue);

        thread.interrupt();

        停止=true;

      }

   }

 public void run()

  { while(true)  

    { byte data[]=new byte[8192];

       DatagramPacket packet=null;

       packet=newDatagramPacket(data,data.length,group,port); 

       try { socket.receive(packet);

             String message=newString(packet.getData(),0,packet.getLength());

             显示正在接收内容.setText("正在接收的内容:\n"+message);

             显示已接收的内容.append(message+"\n");

           }

      catch(Exception e)  { }

      if(停止==true)

           { break;

           }

    }

  }

public static void main(String args[])

  {  new Receive();

  }

}