不会IO流你怎么去玩Socket

netstat指令
netstat -an 可以查看当前的网络情况，包括监听的端口和网络连接的情况
netstat -an | more 分页查看
netstat -anb 显示程序名称

UDP编程

Java里面UDP原理
1，没有服务端和客户端因为他们两个都可以互换
2，DatagramSocket，类似于插口接收数据和发送数据都是通过这个对象完成的，可以指定端口。
3，DatagramPacket，这个是把数据封装到这个对象里面，进行传输

代码块

package udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.nio.charset.StandardCharsets;

public class B {
    public static void main(String[] args) throws IOException {
        //创建接收端
        DatagramSocket datagramSocket = new DatagramSocket(9999);
        //UDP的数据是封装到一个对象里的，创建一个对象去接受
        byte bu[] = new byte[64 * 1024];
        DatagramPacket datagramPacket = new DatagramPacket(bu,0,bu.length);
        //调用send方法准备去接收对象,如果没有对象过来会阻塞
        datagramSocket.receive(datagramPacket);
        //对象过来之后拆包
        byte[] data = datagramPacket.getData();
        int length = datagramPacket.getLength();
        String s = new String(data, 0, length);
        System.out.println(s);

        //到准备去回应
        byte[] bytes = "enen".getBytes(StandardCharsets.UTF_8);
        DatagramPacket datagramPacket1 = new DatagramPacket(bytes,bytes.length, InetAddress.getByName("127.0.0.1"),9998);
        datagramSocket.send(datagramPacket1);
        //关闭资源
        datagramSocket.close();
    }
}

package udp;

import java.io.IOException;
import java.net.*;
import java.nio.charset.StandardCharsets;

public class A {
    public static void main(String[] args) throws IOException {
        //创建发送端
        DatagramSocket datagramSocket = new DatagramSocket(9998);
        //发送数据
        byte[] bytes = "hi,hi".getBytes(StandardCharsets.UTF_8);
        DatagramPacket datagramPacket = new DatagramPacket(bytes,bytes.length, InetAddress.getByName("127.0.0.1"),9999);
        //发送数据
        datagramSocket.send(datagramPacket);
        //去拿数据
        byte bu[] = new byte[64 * 1024];
        DatagramPacket datagramPacket1 = new DatagramPacket(bu,0,bu.length);
        //调用send方法准备去接收对象,如果没有对象过来会阻塞
        datagramSocket.receive(datagramPacket1);
        //对象过来之后拆包
        byte[] data = datagramPacket1.getData();
        int length = datagramPacket1.getLength();
        String s = new String(data, 0, length);
        System.out.println(s);
        //关闭流
        datagramSocket.close();
    }
}

不会IO流你怎么去玩Socket

ps:IO流分字节流和字符流
我们要以内存为参考点[特别容易弄乱]
以内存到[磁盘，网络服务]这种流是输出流
[磁盘，网络服务]到内存这种流是输入流

如图

字节流
OutPutStream 字节输出流，向D盘下面A.txt文件里面写入hi

public class Out {
    public static void main(String[] args) throws IOException {
        File file = new File("D:\\A.txt");
        FileOutputStream fileOutputStream = new FileOutputStream(file);
        fileOutputStream.write("hi".getBytes(StandardCharsets.UTF_8));
        System.out.println("创建成功");
        fileOutputStream.close();
    }
}

InPutStream 字节输入流，我们去读这A.txt文件

public class Out {
    public static void main(String[] args) throws IOException {
       FileInputStream fileInputStream = new FileInputStream(file);
        byte bytes[] = new byte[1024];
        int leng;
        while ((leng = fileInputStream.read(bytes,0,bytes.length)) != -1){
            System.out.println(new String(bytes,0,leng));
        }
    }
}

字符流
Writer 字符输出流

public class Out {
    public static void main(String[] args) throws IOException {
       FileWriter fileWriter = new FileWriter(file);
        fileWriter.write("您好");
    }
}

Reader 字符输入流

public class Out {
    public static void main(String[] args) throws IOException {
      FileReader fileReader = new FileReader(file);
        char chars[] = new char[1024];
        int leng;
        while ((leng = fileReader.read(chars,0,chars.length)) != -1){
            System.out.println(new String(chars,0,leng));
        }
    }
}

记得关闭流