exercise28_2server.java

java程序设计导论（daniel liang著） 所有偶数课后习题答案

// Exercise28_2Server.java
import java.io.*;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Exercise28_2Server extends JFrame {
  private JTextArea jta = new JTextArea();

  public static void main(String[] args) {
    new Exercise28_2Server();
  }

  public Exercise28_2Server() {
    // Place text area on the frame
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);

    // It is necessary to show the frame here!
    setTitle("Exercise28_2Server");
    setSize(500, 300);
    setVisible(true);

    try {
      // Create a server socket
      ServerSocket s = new ServerSocket(8000);
      jta.append("Server started at " + new Date() + '\n');

      // Label a thread
      int i = 0;

      while (true) {
        // Listen for a new connection request
        Socket connectToClient = s.accept();

        // Print the new connect number on the console
        jta.append("Starting thread "+i+" at "+new Date()+'\n');

        // Create a new thread for the connection
        ThreadHandler  t = new ThreadHandler(connectToClient, i);

        // Start the new thread
        t.start();

        // Increment i to label the next connection
        i++;
      }
    }
    catch(IOException ex) {
      System.err.println(ex);
    }
  }

// Inner class
// Define the thread class for handling new connection
class ThreadHandler extends Thread {
  private Socket connectToClient; // A connected socket
  private int counter; // Label for the connection

  public ThreadHandler(Socket c, int i) {
    connectToClient = c;
    counter = i;
  }

  public void run() {
    try {
      // Create data input and print streams
      BufferedReader isFromClient = new BufferedReader(
        new InputStreamReader(connectToClient.getInputStream()));
      PrintWriter osToClient =
        new PrintWriter(connectToClient.getOutputStream(), true);

      // Continuously serve the client
      while (true) {
        // Receive data from the client in string
        StringTokenizer st = new StringTokenizer
          (isFromClient.readLine());

        // Get radius
        double radius = new Double (st.nextToken ()).doubleValue ();
        jta.append("radius received from client: "+radius+'\n');

        // Compute area
        double area = radius*radius*Math.PI;

        // Send area back to the client
        osToClient.println(area);
        jta.append("Area found: "+area+'\n');
      }
    }
    catch(IOException e) {
      System.err.println(e);
    }
  }
}
}