Java_套接字舉例

例題：客戶端輸入圓的半徑併發送給服務器，服務器把計算出的圓的面積返回給客戶。因此可以將計算量大的工作放在服務器端，客戶端負責計算量小的工作，實現客戶端-服務器交互計算來完成任務。
Server.java

package SocketClass.ServerThread;

import java.io.*;
import java.net.*;
import java.util.*;
public class Server {
    public static void main(String []args){
        ServerSocket server = null;
        ServerThread thread;
        Socket you = null;
        while (true){
            try{
                server = new ServerSocket(956);
            }catch (Exception e){
                System.out.println("正在監聽");//ServerSocket對象不能重複創建
            }
            try{
                System.out.println("等待客戶呼叫");
                you = server.accept();
                System.out.println("客戶的地址："+you.getInetAddress());
            }catch (Exception e){
                System.out.println("正在等待客戶");
            }
            if(you!=null){
                new ServerThread(you).start();//爲每個客戶啓動一個專門的線程
            }
        }
    }
}

class ServerThread extends Thread{
    Socket socket;
    DataOutputStream out = null;
    DataInputStream in = null;
    String s = null;
    ServerThread(Socket t){
        socket = t;
        try{
            out = new DataOutputStream(socket.getOutputStream());
            in = new DataInputStream(socket.getInputStream());
        }catch (Exception e){

        }
    }

    public void run(){
        while (true){
            try{
                double r =in.readDouble();//堵塞狀態，除非讀取到信息
                double area = Math.PI*r*r;
                out.writeDouble(area);
            }catch (Exception e){
                System.out.println("客戶離開");
                return;
            }
        }
    }
}

Client.java

package SocketClass.ServerThread;

import java.io.*;
import java.net.*;
import java.util.*;

public class Client {
    public static void main(String []args){
        Scanner scanner = new Scanner(System.in);
        Socket mysocket = null;
        DataInputStream in = null;
        DataOutputStream out = null;
        Thread readData;
        Read read = null;
        try{
            mysocket = new Socket();
            read = new Read();
            readData = new Thread(read);
            System.out.println("輸入服務器的IP：");
            String IP=scanner.nextLine();
            System.out.println("輸入端口號：");
            int port = scanner.nextInt();
            if(mysocket.isConnected()){

            }else {
                InetAddress address = InetAddress.getByName(IP);
                InetSocketAddress socketAddress = new InetSocketAddress(address,port);
                mysocket.connect(socketAddress);
                in = new DataInputStream(mysocket.getInputStream());
                out = new DataOutputStream(mysocket.getOutputStream());
                read.setDataInputStream(in);
                readData.start();
            }
        }catch (Exception e){
            System.out.println("服務器已斷開"+e);
        }
        System.out.println("輸入圓的半徑(放棄請輸入N)：");
        while(scanner.hasNext()){
            double radius = 0;
            try{
                radius = scanner.nextDouble();
            }catch (Exception e){
                System.exit(0);
            }
            try{
                out.writeDouble(radius);
            }catch (Exception e){

            }
        }
    }
}

class Read implements Runnable{

    DataInputStream in;
    public void setDataInputStream(DataInputStream in){
        this.in = in;
    }

    @Override
    public void run() {
        double result = 0;
        while(true){
            try{
                result = in.readDouble();
                System.out.println("圓的面積："+result);
                System.out.println("輸入圓的半徑(放棄請輸入N)：");
            }catch (Exception e){
                System.out.println("與服務器已斷開"+e);
                break;
            }
        }
    }
}

本程序爲了調試方便，在建立套接字連接時，使用的服務器地址是127.0.0.1，如果服務器設置過有效的IP地址，就可以用有效的IP代替程序中的127.0.0.1.