🎶Java网络编程

简介
IP
端口
通信协议
- TCP
- UDP
TCP 连接
- Server 端
- Client 端
文件传输
- Server
- Client
UDP 连接
- Server
- Client
UDP 循环发送
- Server
- Client
双向聊天
URL

简介

架构区分
- 网页编程: B/S
- 网络编程: C/S
通信要素(TCP/IP)
- IP
- 端口
协议参考
更为详细的: 科来网络通讯协议图 2020 版
- 此处针对传输层 TCP/UDP 学习.

IP

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Ip {

  public static void main(String[] args) {
    // write your code here
    try {
      // 获取本机内网IP地址
      InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
      System.out.println(inetAddress1);
      InetAddress inetAddress2 = InetAddress.getByName("localhost");
      System.out.println(inetAddress2);
      InetAddress inetAddress3 = InetAddress.getLocalHost();
      System.out.println(inetAddress3);

      //查询网站ip地址
      InetAddress inetAddress4 = InetAddress.getByName("www.bilibili.com");
      System.out.println(inetAddress4);

      //常用方法
      System.out.println(inetAddress4.getAddress());
      System.out.println(inetAddress4.getCanonicalHostName()); //规范的名字
      System.out.println(inetAddress4.getHostAddress()); //ip
      System.out.println(inetAddress4.getHostName()); //域名，或者自己电脑的名字
    } catch (UnknownHostException e) {
      e.printStackTrace();
    }
  }
  /**
    /127.0.0.1
    localhost/127.0.0.1
    DESKTOP-CTDDD3K/192.168.114.1
    www.bilibili.com/121.17.123.130
    [B@2a3046da
    121.17.123.130
    121.17.123.130
    www.bilibili.com
   */
}

端口

TCP 与 UDP 各有 65535 个端口
- 两个协议间不冲突
- 但是一个协议下的一个端口只能同时被一个软件占用.
端口分类
- 公有端口 0 ~ 1023
  - HTTP：80
  - HTTPS：443
  - FTP：21
  - Telent：23
- 程序注册端口：1024 ~ 49151，分配给用户或者程序
  - Tomcat：8080
  - MySQL：3306
  - Oracle：1512
- 动态、私有：49152 ~ 65535

常用 shell 指令

netstat -ano #查看所有的端口
netstat -ano | finstr "5900" #查看指定的端口
tasklist | findstr "8696" #查看指定端口的进程

InetSocketAddress

import java.net.InetSocketAddress;

public class Port {
  public static void main(String[] args) {
    InetSocketAddress socketAddress = new InetSocketAddress("localhost", 8080);
    System.out.println(socketAddress);

    System.out.println(socketAddress.getAddress());
    System.out.println(socketAddress.getHostName());
    System.out.println(socketAddress.getPort());
  }
  /**
    localhost/127.0.0.1:8080
    localhost/127.0.0.1
    localhost
    8080
  */
}

通信协议

通过约定协议来管控通信的速率,码率等问题
并通过协议分层来简化复杂度
几种协议
- TCP:用户传输协议
- UDP:用户数据报协议
- IP:网络互连协议
- TCP/IP 协议簇:是一组协议 (四层概念模型)

TCP

TCP 是客户端<–>服务端双向的信息沟通,可长时间稳定连接

稳定连接最小验证三次握手,四次挥手

最少需要三次，保证稳定连接！
A：你瞅啥？
B：瞅你咋地？
A：干一场！

至少四次,双方才能都断开连接
A：我要走了
B：你真的要走了吗？
B：你真的真的要走了吗？
A：我真的要走了

UDP

单向的信息传递
没有客户端与服务端界限
无论有没有接收方,无论接收方是否接收,发送方只管发送
常见的DDOS攻击,让大量垃圾信息污染服务器接收端口,使其瘫痪.

TCP 连接

Server 服务端与 Client 客户端通过 TCP 方式创建数据连接.

Server 端

建立服务的端口 ServerScoket
等待用户的连接 accept
接收用户的消息

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

public class Server {
  public static void main(String[] args) throws IOException {
    //1、我得有一个地址
    ServerSocket serverSocket = new ServerSocket(9999);

    while (true) { // 连续接收数据
      //2、等待客户端连接过来
      Socket accept = serverSocket.accept();

      //3、读取客户端的消息
      InputStream inputStream = accept.getInputStream();

      /**
       * 通常IO方式,如果是长数据传输,会导致出错
       *
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) != -1) {
        String s = new String(buffer, 0, length);
        System.out.println(s);
        }
       */

      //4. 管道流接收数据
      ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
      byte[] buffer = new byte[1024];
      int length;
      while ((length = inputStream.read(buffer)) != -1) {
        byteArrayOutputStream.write(buffer, 0, length);
      }
      if (byteArrayOutputStream.toString().matches("quit")) {
        break;
      } else {
        System.out.println(byteArrayOutputStream.toString());
        byteArrayOutputStream.close();
        inputStream.close();
        accept.close();
      }
    }

    //5. 最后关闭
    serverSocket.close();
  }
}

Client 端

连接服务器 Socket
发送消息

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

public class Client {
  public static void main(String[] args) throws Exception {
    //1、要知道服务器的地址，端口号
    InetAddress address = InetAddress.getLocalHost();

    int port = 9999;

    //2、创建一个socket连接
    Socket socket = new Socket(address, port);

    //3、发送消息 IO流
    OutputStream outputStream = socket.getOutputStream();
    outputStream.write("Weidows connecting here.".getBytes());
    // outputStream.write("quit".getBytes());

    //4.关闭通道
    outputStream.close();
    socket.close();
  }
}

文件传输

Server

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
  public static void main(String[] args) throws Exception {
    //1、创建服务
    ServerSocket serverSocket = new ServerSocket(9999);

    //2、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
    System.out.println("Server开始监听.");

    //3、获取输入流
    InputStream is = socket.getInputStream();

    //4、文件输出
    FileOutputStream fos = new FileOutputStream(new File("Java/src/main/java/twenty_one/net/file_upload/receive.png"));
    byte[] buffer = new byte[1024];
    int len;
    while ((len = is.read(buffer)) != -1) {
      fos.write(buffer, 0, len);
    }
    System.out.println("Server接收完毕.");

    //通知客户端我接收完毕了
    OutputStream os = socket.getOutputStream();
    os.write("Server通知:接受完毕，Client可以断开了".getBytes());

    //5、关闭资源
    fos.close();
    is.close();
    socket.close();
    serverSocket.close();
    System.out.println("Server已发送验证并断开连接.");
  }
  /**
    Server开始监听.
    Server接收完毕.
    Server已发送验证并断开连接.
   */
}

Client

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

public class Client {
  public static void main(String[] args) throws Exception {
    //1、创建一个Socket连接
    Socket socket = new Socket(InetAddress.getByName("localhost"), 9999);

    //2、创建一个输出流
    OutputStream os = socket.getOutputStream();

    //3、读取文件
    FileInputStream fis = new FileInputStream(new File("Java/src/main/java/twenty_one/net/file_upload/upload.png"));

    //4、写出文件
    byte[] buffer = new byte[1024];
    int len;
    while ((len = fis.read(buffer)) != -1) {
      os.write(buffer, 0, len);
    }
    System.out.println("Client传输完毕.");

    //通知服务器，我已经结束了
    socket.shutdownOutput(); //我已经传输完了！

    //确定服务器接收完毕，才能够断开连接
    InputStream inputStream = socket.getInputStream();
    //String byte[]
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] buffer2 = new byte[1024];
    int len2;
    while ((len2 = inputStream.read(buffer2)) != -1) {
      baos.write(buffer2, 0, len2);
    }
    System.out.println(baos.toString());

    //5、关闭资源
    baos.close();
    inputStream.close();
    fis.close();
    os.close();
    socket.close();
    System.out.println("Client已接收到验证并断开连接");
  }
  /**
    Client传输完毕.
    Server通知:接受完毕，Client可以断开了
    Client已接收到验证并断开连接
   */
}

UDP 连接

Server

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

public class Server {
  public static void main(String[] args) throws Exception {
    // 1.开放端口
    DatagramSocket datagramSocket = new DatagramSocket(9999);
    System.out.println("等待数据传入中...");

    // 2.接收数据
    byte[] buffer = new byte[1024];
    DatagramPacket datagramPacket = new DatagramPacket(buffer, buffer.length);
    datagramSocket.receive(datagramPacket); //阻塞接收

    // 3.输出
    System.out.println("Server接收到数据:" + new String(datagramPacket.getData()));

    // 4.关闭
    datagramSocket.close();
  }
}

Client

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

public class Client {
  public static void main(String[] args) throws Exception {
    // 1.创建数据包
    InetAddress localHost = InetAddress.getLocalHost();
    int port = 9999;
    byte[] data = "这是Client发送的数据.".getBytes();
    DatagramPacket datagramPacket = new DatagramPacket(data, data.length, localHost, port);

    // 2.创建Socket
    DatagramSocket datagramSocket = new DatagramSocket();

    // 3.发送数据
    datagramSocket.send(datagramPacket);
    System.out.println("传输成功.");

    // 4.关闭连接
    datagramSocket.close();
  }
}

UDP 循环发送

Server

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

public class Server2 {
  public static void main(String[] args) throws Exception {
    // 1.准备连接
    DatagramSocket datagramSocket = new DatagramSocket(9999);
    while (true) {
      byte[] bytes = new byte[1024];
      DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length);
      System.out.println("Server准备接收数据中.");

      // 2.接收数据
      datagramSocket.receive(datagramPacket);
      String string = new String(datagramPacket.getData());
      System.out.println("接收到数据:\t" + datagramPacket.getAddress() + ":" + datagramPacket.getPort() + "\t" + string);

      // 这里的string="quitxxxxxxxxxxxxxx",总长为上面的1024,用.equals()无法判断.
      if (string.contains("quit")) {
        break;
      }
    }

    // 3.断开连接
    datagramSocket.close();
    System.out.println("Server已关闭连接.");
  }
}

Client

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

public class Client2 {
  public static void main(String[] args) throws Exception {
    // 0.准备连接
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
    DatagramSocket datagramSocket = new DatagramSocket();

    while (true) {
      // 1.准备数据
      System.out.println("Client准备读取Terminal数据:");
      String readLine = bufferedReader.readLine();
      byte[] bytes = readLine.getBytes();
      DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length, new InetSocketAddress("localhost", 9999));

      // 2.发送数据
      datagramSocket.send(datagramPacket);
      System.out.println("Client已经发送数据.");

      if (readLine.equals("quit")) {
        break;
      }
    }

    // 3.断开连接
    datagramSocket.close();
    System.out.println("Client已关闭连接.");
  }
}

双向聊天

实现发送,接收两个线程类
老师和学生各开上面两个线程,实现发,收功能.

发送线程

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

public class TalkSend implements Runnable {
  BufferedReader bufferedReader = null;
  DatagramSocket datagramSocket = null;

  private String targetIP;
  private int targetPort;

  public TalkSend(String targetIP, int targetPort) {
    this.targetIP = targetIP;
    this.targetPort = targetPort;

    try {
      // 0.准备连接
      bufferedReader = new BufferedReader(new InputStreamReader(System.in));
      datagramSocket = new DatagramSocket();
    } catch (SocketException e) {
      e.printStackTrace();
    }
  }

  public static void main(String[] args) {

  }

  @Override
  public void run() {
    while (true) {
      // 1.准备数据
      System.out.println("Client准备读取Terminal数据:");
      try {
        String readLine = bufferedReader.readLine();
        byte[] bytes = readLine.getBytes();
        DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length,
            new InetSocketAddress(targetIP, targetPort));

        // 2.发送数据
        datagramSocket.send(datagramPacket);
        System.out.println("Client已经发送数据.");

        if (readLine.equals("quit")) {
          break;
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }

    // 3.断开连接
    datagramSocket.close();
    System.out.println("Client已关闭连接.");
  }
}

接收线程

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class TalkReceive implements Runnable {
  DatagramSocket datagramSocket = null;
  private int localPort;

  public TalkReceive(int localPort) {
    this.localPort = localPort;

    try {
      datagramSocket = new DatagramSocket(this.localPort);
    } catch (SocketException e) {
      e.printStackTrace();
    }
  }

  @Override
  public void run() {
    // 1.准备连接
    while (true) {
      try {
        byte[] bytes = new byte[1024];
        DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length);
        System.out.println("Server准备接收数据中.");

        // 2.接收数据
        datagramSocket.receive(datagramPacket);

        String string = new String(datagramPacket.getData());
        System.out.println("接收到数据:\t" + datagramPacket.getAddress() + ":" + datagramPacket.getPort() + "\t" + string);

        // 这里的string="quitxxxxxxxxxxxxxx",总长为上面的1024,用.equals()无法判断.
        if (string.contains("quit")) {
          break;
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }

    // 3.断开连接
    datagramSocket.close();
    System.out.println("Server已关闭连接.");
  }

  public static void main(String[] args) {

  }
}

老师

public class Teacher {
  public static void main(String[] args) {
    // 老师
    new Thread(new TalkReceive(7777)).start();
    new Thread(new TalkSend("localhost", 8888)).start();
  }
  /**
    Server准备接收数据中.
    Client准备读取Terminal数据:
    接收到数据:     /127.0.0.1:50277        15465
    Server准备接收数据中.
    123456
    Client已经发送数据.
    Client准备读取Terminal数据:
   */
}

学生

public class Student {
  public static void main(String[] args) {
    // 学生
    new Thread(new TalkReceive(8888)).start();
    new Thread(new TalkSend("localhost", 7777)).start();
  }
  /**
    Server准备接收数据中.
    Client准备读取Terminal数据:
    15465
    Client已经发送数据.
    Client准备读取Terminal数据:
    接收到数据:     /127.0.0.1:50279        123456
    Server准备接收数据中.
   */
}

URL

文件下载

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

public class GetURL {
  public static void main(String[] args) throws Exception {
    // 1.设置URL和文件路径
    URL url = new URL("https://pan.weidows.tech/d/local/img/divider.png");
    String path = "Java/src/main/java/twenty_one/net/";
    String fileName = url.getPath().substring(url.getPath().lastIndexOf('/') + 1);

    /**
     * ! URL类用法
     *
      System.out.println(url.getProtocol());
      System.out.println(url.getHost());
      System.out.println(url.getPort());
      System.out.println(url.getPath());
      System.out.println(url.getFile());
      System.out.println(url.getQuery());
    */

    // 2.输入输出流
    InputStream openStream = url.openStream();
    FileOutputStream fileOutputStream = new FileOutputStream(new File(path + fileName));

    // 3.传输数据
    byte[] bytes = new byte[1024];
    int length;
    while ((length = openStream.read(bytes)) != -1) {
      fileOutputStream.write(bytes, 0, length);
    }

    // 4.关闭连接
    fileOutputStream.close();
    openStream.close();
  }
}

🎶Java网络编程

简介

IP

端口

通信协议

TCP

UDP

TCP 连接

Server 端

Client 端

文件传输

Server

Client

UDP 连接

Server

Client

UDP 循环发送

Server

Client

双向聊天

发送线程

接收线程

老师

学生

URL

-> 欢迎,锟斤拷! <-

低情商：代码一坨屎
高情商：兼容性极强

简介

IP

端口

通信协议

TCP

UDP

TCP 连接

Server 端

Client 端

文件传输

Server

Client

UDP 连接

Server

Client

UDP 循环发送

Server

Client

双向聊天

发送线程

接收线程

老师

学生

URL

-> 欢迎,锟斤拷! <-

低情商：代码一坨屎高情商：兼容性极强

低情商：代码一坨屎
高情商：兼容性极强