网络编程知识

网络编程

概述

• 计算机网络

  计算机网络是指将[地理位置]不同的具有独立功能的多台计算机及其外部设备，通过[通信线路]和通信设备连接起来，在网络操作系统，网络管理软件及网络通信协议的管理和协调下，实现资源共享和信息传递的计算机系统

• 网络通信的要素

  • IP和端口号

  • 网络通信协议

IP地址

• IP地址：inetAddress

//测试IP
public class TestInetAddress {
    public static void main(String[] args) {
        try {
            //查询本机地址
            InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
            System.out.println(inetAddress1);
            InetAddress inetAddress3 = InetAddress.getLocalHost();
            System.out.println(inetAddress3);
            //查询网站Ip地址
            InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress2);
            
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

端口

• 表示计算机上的一个程序的进程

  • 不同的进程有不同的端口号

  • 同一个协议下，端口号不能冲突

• 端口分类

  • 共有端口 0-1023

    • HTTP：80

    • HTTPS:443

  • 程序注册端口 1024-49151

    • Tomcat：8080

    • MySQL:3309

    • Oracle：1521

  • 动态 ，私有：49152-65535

public class TestInetSockAddress {
    public static void main(String[] args) {
        InetSocketAddress inetSocketAddress1 = new InetSocketAddress("127.0.0.1", 8080);
        System.out.println(inetSocketAddress1);
        InetSocketAddress inetSocketAddress2 = new InetSocketAddress("localhoet", 8080);
        System.out.println(inetSocketAddress2);
    }
}

通信协议

• TCP/IP协议簇：实际上是一组协议

  • TUP :用户传输协议

  • UDP:用户数据报协议

    • 出名的协议

      • TCP

      • IP：网络互连协议

TCP实现聊天

//客户端
public class TestTcpClient {
    public static void main(String[] args) throws Exception{
            //要知道服务器的地址
            InetAddress serverIp = InetAddress.getByName("127.0.0.1");
            //端口号
            int port=9999;
            //创建一个socket连接
            Socket socket = new Socket(serverIp,port);
            //发送消息 IO流
            OutputStream outputStream = socket.getOutputStream();
            outputStream.write("林夕的花海".getBytes());
            outputStream.close();
    }
}
===============================================
    //服务端/客户端
public class TestTcpServer {
    public static void main(String[] args) throws Exception{
        ServerSocket serverSocket = new ServerSocket(9999);
        //等待客户端连接过来
        Socket socket = serverSocket.accept();
        //读取客户端的消息
        InputStream inputStream = socket.getInputStream();
        //管道流
        ByteArrayOutputStream baos  = new ByteArrayOutputStream();
        byte[] buf=new byte[1024];
        int len;
        while((len=inputStream.read(buf))!=-1){
            baos.write(buf,0,len);
        }
        System.out.println(baos.toString());
        inputStream.close();
    }
}

TCP实现文件上传

//服务端
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class TestTcpServer1 {
    public static void main(String[] args) throws Exception{
        //创建服务
        ServerSocket serverSocket = new ServerSocket(9000);
        //监听客户端的连接
        Socket socket = serverSocket.accept();//阻塞式监听，会一直等待客户端连接
        //获取输入流
        InputStream is = socket.getInputStream();
        //文件输出
        //管道输出流
        FileOutputStream fos = new FileOutputStream(new File("receive.png"));
        byte[] buf = new byte[1024];
       int len;
       while((len=is.read(buf))!=-1){
           fos.write(buf,0,len);
       }
       //通知客户端我接收完毕了
        OutputStream os  = socket.getOutputStream();
       os.write("我接收完毕了".getBytes());
        fos.close();
        socket.close();
        serverSocket.close();
    }
}
==========================================================
    //客户端
import java.io.*;
import java.net.InetAddress;
import java.net.Socket;

public class TestTpcClient1 {
    public static void main(String[] args) throws Exception {
        //创建一个Socket连接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9000);
        //创建一个输出流
        OutputStream os  = socket.getOutputStream();
        //文件流
        FileInputStream fis  = new FileInputStream(new File("" +
                "C:\\Users\\31016\\Pictures\\Screenshots\\屏幕截图 2023-06-10 194502.png"));
        //读取文件
        byte[] buf = new byte[1024];
        int len;
        while((len=fis .read(buf))!=-1){
           os.write(buf,0,len);
        }
        //通知服务器，我已经结束
        socket.shutdownOutput();//已将传输完了
        //确认服务器接收完毕，才能断开连接
        InputStream inputStream = socket.getInputStream();
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        byte[] buf2 = new byte[1024];
        int len2;
        while((len2=inputStream.read(buf2))!=-1){
            byteArrayOutputStream.write(buf2,0,len2);
        }
        System.out.println(byteArrayOutputStream.toString());
        fis.close();
        socket.close();
        os.close();
    }
}

 

UDP

UDP实现发送消息

import java.net.DatagramPacket;
import java.net.DatagramSocket;
//服务端
public class TestUdpServer {
    public static void main(String[] args) throws Exception{
        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buf = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buf, 0, buf.length);
        socket.receive(packet);//阻塞接受
        System.out.println(new String(packet.getData(),0,packet.getLength()));
        //关闭连接
        socket.close();
    }
}
==================================
   //客户端
 import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

//不需要连接服务器
public class TestUdpClient {
    public static void main(String[] args) throws Exception{
        //建立一个Socket
        DatagramSocket socket = new DatagramSocket();
        //建立一个包
        String msg="林夕的花海";
        InetAddress inetAddress = InetAddress.getByName("localhost");
        int port=9090;
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), msg.getBytes().length, inetAddress, port);
        //发送一个包
        socket.send(packet);
        //关闭包
        socket.close();
    }
}

 

循环发送消息

• 两个人都可以是接收方与发送方

import java.net.DatagramPacket;
import java.net.DatagramSocket;
//接收端
public class TestUdpReceive {
    public static void main(String[] args) throws Exception{
        DatagramSocket socket = new DatagramSocket(6666);
        while(true){
            byte[] container= new byte[1024];
            DatagramPacket packet = new DatagramPacket(container, 0, container.length);
            socket.receive(packet);
            //断开重连
            byte[] data = packet.getData();
            String receiveData=new String(data,0, data.length);
            System.out.println(receiveData.toString());
            if (receiveData.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}
=======================================
    //发送端
    import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class TestUdpSender {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);
        //准备数据，控制台读取 Syste.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("localhost", 6666));
            socket.send(packet);
            if (data.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

UDP多线程在线咨询

public class TalkSender implements Runnable{
    DatagramSocket socket =null;
    BufferedReader reader ;
    private int fromPort;
    private String toIp;
    private int toPort;

    public TalkSender(int fromPort, String toIp, int toPort) {
        this.fromPort = fromPort;
        this.toIp = toIp;
        this.toPort = toPort;
        try {
             socket = new DatagramSocket(fromPort);
            reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (SocketException e) {
           e.printStackTrace();
        }
    }

    @Override
    public void run() {
        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 (IOException e) {
               e.printStackTrace();
            }
        }
        socket.close();
    }
}
-----------------------------------------------------------------
    
    public class TalkReceive implements Runnable{
    DatagramSocket socket ;
    private int port;
    private  String msgForm;

    public TalkReceive(int port,String msgForm) {
        this.port = port;
        this.msgForm=msgForm;
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            throw new RuntimeException(e);
        }
    }
    @Override
    public void run() {
        while(true){
            try {
                byte[] container= new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
                socket.receive(packet);
                //断开重连
                byte[] data = packet.getData();
                String receiveData=new String(data);
                System.out.println(msgForm+":"+receiveData);
                if (receiveData.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        socket.close();
    }
}
---------------------------------------------
    public class TalkStudent {
    public static void main(String[] args) {
        //开启两个线程
        new  Thread(new TalkSender(7777,"localhost",9999)).start();
        new Thread(new TalkReceive(8888,"老师")).start();
    }
}
--------------------------------------------
    public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkSender(5555,"localhost",8888)).start();
        new Thread(new TalkReceive(9999,"老师")).start();
    }
}