网络编程

1.URL
有时间把这么想明白这种操作流的过程

public static void main(String[] args)throws Exception{
        URL url = new URL("http://www.baidu.com");
        InputStreamReader isr = new InputStreamReader(url.openStream());
        BufferedReader br = new BufferedReader(isr);
        String s;
        while((s = br.readLine()) != null){
            System.out.println(s);
        }
        br.close();
    }

还有一种方式，就是给服务器传数据，然后服务器会送给客户端数据。上面是最简单的一种。
2.Socket

服务多个用户（TCP实现）

package com.dgg.socket2;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

class ServerWorker extends Thread{
    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;
    public ServerWorker(Socket s) throws IOException{
        socket = s;
        in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()), true);
        start();
    }
    public void run(){
        try {
            while(true){
                String str = in.readLine();//从in读数据
                if(str.equals("END"))
                    break;
                System.out.println("来自客户端: " + str);
                out.println(str);
                Thread.sleep(3000);//将来自客户端的数据，原封不动传回
            }
            System.out.println("关闭...");
        }catch (IOException e){

        }catch (InterruptedException e){
            e.printStackTrace();
        }finally {
            try{
                socket.close();
            }catch (IOException e){

            }
        }
    }
}
public class ServerSocketMult {
    static final int ROPT = 8080;
    public static void main(String[] args) throws IOException{
        ServerSocket s = new ServerSocket(ROPT);
        System.out.println("启动服务器");
        try{
            while(true){
                Socket socket = s.accept();
                try{
                    new ServerWorker(socket);
                }catch (IOException e){
                    socket.close();
                }
            }
        }finally {
            s.close();
        }
    }
}

package com.dgg.socket2;

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;

class ClientSocketMultThread extends Thread {
    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;
    private static int counter = 0;
    private int id = ++ counter;

    public static int threadCount(){
        return counter;
    }

    public ClientSocketMultThread(InetAddress addr){
        System.out.println("创建客户端: " + id);
        try{
            socket = new Socket(addr, ServerSocketMult.ROPT);
        }catch (IOException e){

        }
        try{
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()), true);
            start();
        }catch (IOException e){
            try{
                socket.close();
            }catch (IOException e2){

            }
        }
    }

    public void run(){
        try{
            for (int i = 0; i < 5; i++) {
                out.println("客户端 " + id +  ": 消息 " + i);//向out写数据
                String str = in.readLine();//从in读返回的数据
                System.out.println("来自服务器: " + str);
            }
            out.println("END");
        }catch (IOException e){

        }finally {
            try{
                socket.close();
            }catch (IOException e){

            }
        }
    }
}
    public class ClientSocketMult {
        static final int MAX_THREAD = 10;
            public static void main(String[] args) throws IOException, InterruptedException{//内部类里不能出现static声明
                InetAddress addr = InetAddress.getByName(null);
                while(true){
                    if(ClientSocketMultThread.threadCount() < MAX_THREAD){
                        new ClientSocketMultThread(addr);
                    }
                    Thread.sleep(5000); //每5秒建一个客户端？访问自己加的服务器
                }
            }
    }

数据报通信（UDP）

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