[网络协议]Java网络编程

TCP实现网络通信

服务端

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

//服务端
public class TCPServerDemo01 {
    public static void main(String[] args) {
        //我要有一个地址
        try {
            ServerSocket serverSocket = new ServerSocket(9999);  //套接字，Java网络编程也称为套接字编程
            //2.等待客户端连接过来
            Socket socket = serverSocket.accept();
            //3.读取客户端信息
            InputStream is = socket.getInputStream();

            /*

             */
//            byte[] buffer = new byte[1024];
//            int len;
//            while ((len = is.read(buffer))!= -1){
//                String msg = new String(buffer,0,len);
//                System.out.println(msg);
//            }

            //管道流
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024];
            int len;
            while ((len = is.read(buffer)) != -1){
                baos.write(buffer,0,len);
            }
            System.out.println(baos.toString());
            baos.close();
            is.close();
            socket.close();
            serverSocket.close();


        } catch (IOException e) {
            e.printStackTrace();
        }finally {

        }
    }
}

客户端

package tcpChatting;

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


//客户端
public class TCPClientDemo01 {
    public static void main(String[] args) {
        //1.要知道服务器的地址
        try {
            InetAddress serverIP = InetAddress.getByName("192.168.3.12");
            //2.需要端口号
            int port = 9999;
            //3.创建一个Socket连接
            Socket socket = new Socket(serverIP, port);
            //4.发送消息IO流
            OutputStream os = socket.getOutputStream();
            os.write("你好，欢迎学习Java Web编程！".getBytes());
            os.close();

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

Tomcat

服务端

• 自定义S
• Tomcat服务器S
  客户端
• 自定义C
• 浏览器B

UDP消息发送

类似发短信，不用建立连接，但是要知道对方的地址。

package UDPTest;


import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

//不需要连接服务器
public class UDPClientDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立一个Socket
        DatagramSocket socket = new DatagramSocket();
        //2.创建一个包
        String msg="号的";

        //发送给谁
        InetAddress address = InetAddress.getByName("192.168.3.174");
        int port = 9090;
        //3.发送包

        //==============================================数据-----数据起始位置---数据长度----IP地址---端口号
        DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.length(),address,port);
        socket.send(packet);

        //关闭流
        socket.close();
    }
}

接收消息

package UDPTest;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPServerDemo01 {
    public static void main(String[] args) throws Exception {
        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);  //接收
        socket.receive(packet);  //阻塞接收
        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0,packet.getLength()));
        socket.close();
    }
}

UDP聊天实现

循环发送消息

package UDPChatting;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class UDPSenderDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);

        //准备数据,控制台读取System.in
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String data = reader.readLine();
            byte[] datas = data.getBytes();
            DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress("172.17.218.109", 6666));
            socket.send(packet);
            if(data.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

循环接收消息

package UDPChatting;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPReceiveDemo01 {
    public static void main(String[] args) throws Exception{
        DatagramSocket socket = new DatagramSocket(6666);
        while (true) {
            //准备接收的方法
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container, 0, container.length);
            socket.receive(packet);  //阻塞式接收

            //断开连接 bye
            byte[] data = packet.getData();
            String receive_data = new String(data,0,data.length);
            System.out.println(receive_data);
            if(receive_data.equals("bye")){
                break;
            }


        }
        socket.close();
    }
}

在线两个人都可以是发送方，都可以是接收方。

接收代码

package UDPChatting;

import java.net.DatagramPacket;
import java.net.DatagramSocket;


public class TalkReceive implements Runnable{
    DatagramSocket socket= null;
    private String msgFrom;
    private int port;

    public TalkReceive(int port, String msgFrom) {
        this.port = port;
        this.msgFrom = msgFrom;
        try {
            socket = new DatagramSocket(port);
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        while (true) {
            try {
                //准备接收的方法
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
                socket.receive(packet);  //阻塞式接收

                //断开连接 bye
                byte[] data = packet.getData();
                String receive_data = new String(data, 0, data.length);
                System.out.println(msgFrom+":"+receive_data);
                if (receive_data.trim().equals("bye")) {
                    break;
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

发送代码

package UDPChatting;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class TalkSend implements Runnable{
    DatagramSocket socket = null;
    BufferedReader reader = null;

    private String fromIP;
    private String toIP;
    private int toPort;
    private int fromPort;

    public TalkSend(String fromIP, String toIP, int toPort, int fromPort) {
        this.fromIP = fromIP;
        this.toIP = toIP;
        this.toPort = toPort;
        this.fromPort = fromPort;
        try {
            socket = new DatagramSocket(fromPort);
            reader = new BufferedReader(new InputStreamReader(System.in));
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        //准备数据,控制台读取System.in
        while (true) {
            try{
                String data = reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress(this.toIP, this.toPort));
                socket.send(packet);
                if(data.equals("bye")){
                    break;
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

开启多线程进行即时聊天。

package UDPChatting;

public class TalkStudent {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend("192.168.3.136"," 172.17.218.109",9999,7777)).start();
        new Thread(new TalkReceive(8888,"老师")).start();
    }
}

另一端

package UDPChatting;

public class TalkTeacher {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend("192.168.3.136","192.168.3.136",8888,5555)).start();
        new Thread(new TalkReceive(9999,"学生")).start();
    }
}

URL

https://www.baidu.com
统一资源定位符，用来定位资源的，定位互联网上的某一个资源。

协议：//ip地址:端口号/项目名/资源

package URLTest;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class URLDownload {
    public static void main(String[] args) throws Exception {
        //1.下载地址
        URL url = new URL("https://gitee.com/dinglide/Dummy-Robot/raw/main/5.Docs/1.Images/dummy.jpg");

        //2.连接到资源
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("dummy.jpg");

        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len = inputStream.read(buffer)) != -1){
            fos.write(buffer,0,len);  //写出这个程序
        }

        fos.close();
        inputStream.close();
        urlConnection.disconnect(); //断开连接
    }
}