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一篇文章帶你入門java網(wǎng)絡(luò)編程

更新時間：2021年08月04日 14:39:16 作者：正函數(shù)-

網(wǎng)絡(luò)編程是指編寫運行在多個設(shè)備（計算機）的程序，這些設(shè)備都通過網(wǎng)絡(luò)連接起來。本文介紹了一些網(wǎng)絡(luò)編程基礎(chǔ)的概念，并用Java來實現(xiàn)TCP和UDP的Socket的編程，來讓讀者更好的了解其原理

基于TCP/IP協(xié)議的通信

TCP/IP協(xié)議
- TCP/IP協(xié)議.會在通信兩端建立連接（虛擬連接），用于發(fā)送和接收數(shù)據(jù)
- TCP/IP協(xié)議是一種可靠的網(wǎng)絡(luò)協(xié)議，它通過重發(fā)機制來保證這種可靠性

通信的實現(xiàn)

ServerSocket用來監(jiān)聽來自客戶端的連接，當(dāng)沒有連接時，它處于阻塞狀態(tài)

客戶端使用Socket連接到指定的服務(wù)器

基于UDP協(xié)議的通信

UDP協(xié)議
- UDP協(xié)議不會在通信兩端建立連接（虛擬鏈路），而是直接發(fā)送連接
- UDP協(xié)議是一種不可靠的網(wǎng)絡(luò)協(xié)議，但是這種協(xié)議的通信效率非常高
通信的實現(xiàn)
- DatagramSocket用于兩端的通信，它不負責(zé) 維護狀態(tài)，不產(chǎn)生io流，僅僅是發(fā)送或接受數(shù)據(jù)包
- DatagramPacket代表數(shù)據(jù)包

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InetAddress

/**
 *
 * InetAddressDemo
 *
 *
 */

public class InetAddressDemo {

    public static void main(String[] args) throws IOException {
        InetAddress baidu = InetAddress.getByName("www.baidu.com");
        System.out.println(baidu);
        System.out.println(baidu.getHostAddress());//獲取主機地址
        System.out.println(baidu.isReachable(1000));//是否可達
        System.out.println("====================================================================================");
        InetAddress local = InetAddress.getByAddress(new byte[]{127, 0, 0, 1});
        System.out.println(local.getHostName());//獲取主機名
        System.out.println(local.isReachable(1000));//是否可達
    }
}

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案例演示（簡易聊天室）

package javaserver.TcpServer;
import JAVAClient.TcpClient;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class tcpServer {
    public static ExecutorService threadPool= Executors.newFixedThreadPool(10);
    public static List<Socket> socketList= Collections.synchronizedList(new ArrayList<>());
    public static void main(String[] args) {
//
//        try {
//
//            //接受客戶端的請求
//            ServerSocket serverSocket=new ServerSocket(9000);
//            while (true){
//                Socket socket = serverSocket.accept();//封裝了一些客戶端的信息
//                System.out.println("請求;" + socket.toString());
//
//                PrintStream ps=new PrintStream(socket.getOutputStream());
//                ps.println("welcome "+ socket.getInetAddress().getHostAddress());
//                socket.close();
//            }
//
//        } catch (Exception e) {
//            e.printStackTrace();
//        }
//    }
        try {
            ServerSocket serverSocket = new ServerSocket(9000);
            while (true){
                Socket socket = serverSocket.accept();
                socketList.add(socket);
                threadPool.submit(new ThreadTask(socket));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}
class  ThreadTask implements  Runnable{
    private Socket  socket;
    private BufferedReader reader;
    public ThreadTask(Socket socket) {
        this.socket = socket;
        try {
            this.reader=new BufferedReader(new InputStreamReader(socket.getInputStream()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void run() {
        try {
            String line;
            while ((line=reader.readLine())!=null){
                for (Socket client: tcpServer.socketList){
                    String from=socket.getInetAddress().getHostAddress()+":::"+socket.getPort();
                    String content= from+"說"+line;
                    new PrintStream(client.getOutputStream()).println(content);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package JAVAClient;
import java.io.*;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TcpClient {
    public static ExecutorService threadPool= Executors.newFixedThreadPool(3);
    public static void main(String[] args) throws IOException {
//        Socket socket=new Socket("127.0.0.1",9000);
//        BufferedReader br=new BufferedReader(new InputStreamReader(socket.getInputStream()));
//        String s = br.readLine();
//        System.out.println(s);
        Socket socket=new Socket("127.0.0.1",9000);
        threadPool.submit(new ReadTask(socket));
        threadPool.submit(new WriteTask(socket));


    }
}

class ReadTask implements Runnable{
   private Socket socket;
   private BufferedReader reader;
    public ReadTask(Socket socket) {
        this.socket = socket;
        try {
            this.reader=new BufferedReader(new InputStreamReader(socket.getInputStream()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void run() {
        try {
            String line;
            while ((line=reader.readLine())!=null){
                System.out.println(line);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class WriteTask implements Runnable{
    private Socket socket;
    private PrintStream writer;
    public WriteTask(Socket socket) {
        this.socket = socket;
        try {
            writer=new PrintStream(socket.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void run() {
        Scanner scanner = new Scanner(System.in);
        String line;
        while ((line=scanner.nextLine())!=null){
            writer.println(line);
        }
    }
}

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UDP 演示

服務(wù)端

package javaserver.TcpServer;
import java.net.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class UdpServer {

    public static ExecutorService threadPool= Executors.newFixedThreadPool(10);
    public static List<InetSocketAddress> addressesList=new ArrayList<>();

    public static void main(String[] args) {
        try {
            DatagramSocket socket=new DatagramSocket(9001);
            // 隨時通知
            threadPool.submit(new SendTask(socket));
            //接受訪問 并且記錄
            byte[] buffer=new byte[1024];
            DatagramPacket packet=new DatagramPacket(buffer,buffer.length);
            while (true){
                socket.receive(packet);
                addressesList.add((InetSocketAddress) packet.getSocketAddress());
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class SendTask implements Runnable{
    private DatagramSocket socket;
    public SendTask(DatagramSocket socket) {
        this.socket = socket;
    }
    @Override
    public void run() {
        try {
            Scanner scanner = new Scanner(System.in);
            String line;
            while ((line= scanner.nextLine())!=null){
                for (InetSocketAddress isa:UdpServer.addressesList){
                    byte[] buffer=line.getBytes();
                    DatagramPacket packet=new DatagramPacket(buffer,buffer.length,isa.getAddress(),isa.getPort());
                    socket.send(packet);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

客戶端

package JAVAClient;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class UdpClient {
    public static ExecutorService threadPool= Executors.newFixedThreadPool(3);
    public static void main(String[] args) {
        try {
            DatagramSocket socket=new DatagramSocket();
//            注冊
             DatagramPacket packet=new DatagramPacket(new byte[]{1},1, InetAddress.getByName("127.0.0.1"),9001);
             socket.send(packet);
//             接收
            threadPool.submit(new ReceiveTask(socket));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}
class ReceiveTask implements Runnable{
    private DatagramSocket socket;
    public ReceiveTask(DatagramSocket socket) {
        this.socket = socket;
    }
    @Override
    public void run() {
   try {
       byte[] buffer=new  byte[1024];
       DatagramPacket packet=new DatagramPacket(buffer,buffer.length);
       while (true){
           socket.receive(packet);
           String line =new String(packet.getData(),0, packet.getLength());
           System.out.println(line);
       }
   } catch (Exception e) {
       e.printStackTrace();
   }
    }
}

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