如何通过 UDP 数据报将 ByteArray 转换为 int

Question

我的客户代码：

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.Scanner;

public class UDPClient {
    public static void main (String[] args) throws IOException{

        DatagramSocket ds = new DatagramSocket();

        System.out.println("Insert number: ");  
        Scanner s= new Scanner(System.in);
        int num = s.nextInt();

        byte[] byteSend = ByteBuffer.allocate(4).putInt(num).array();
        InetAddress address = InetAddress.getByName("localhost");
        int port = 1999;
        DatagramPacket dpSend = new DatagramPacket(byteSend, byteSend.length , address ,port);
        ds.send(dpSend);

        byte[] byteReceive = new byte[1];
        byte[] byteAck = "*".getBytes();
        DatagramPacket dpReceive = new DatagramPacket(byteReceive, byteReceive.length);
        DatagramPacket dpAck = new DatagramPacket(byteAck, byteAck.length , address, port);

        for (int i=1; i<=num; i++){
            ds.receive(dpReceive);
            String randomString = new String(dpReceive.getData());
            System.out.println(randomString);
            ds.send(dpAck);
        }
        ds.close();
    }
}

我的服务器代码：

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.nio.ByteBuffer;

public class UDPServer {

    public static void main(String[] args) throws IOException {



        DatagramSocket ds = new DatagramSocket(1999);
        while (true) {
            byte[] byteReceive = new byte[4]; //size of type int: 4 bytes
            DatagramPacket dp = new DatagramPacket(byteReceive, byteReceive.length);
            ds.receive(dp);
            int num = ByteBuffer.wrap(dp.getData()).getInt();

            InetAddress address = dp.getAddress();
            int port = dp.getPort();
            byte[] byteSend = "&&&&&".getBytes();

            Byte b = rno[0]; // Boxing conversion converts `byte` to `Byte`
            int i = b.intValue();


            DatagramPacket dpSend = new DatagramPacket(byteSend, byteSend.length, address, port);

            byte[] byteAck = new byte[1];
            DatagramPacket dpAck = new DatagramPacket(byteAck, byteAck.length);

            for (int i = 1; i <= num; i++) {
                ds.send(dpSend);
                ds.receive(dpAck);

                String stringAck = new String(dpAck.getData());
                if (!"*".equals(stringAck)) {
                    System.out.println("Error!");
                    return;
                }
            }
        }
    }
}

我喜欢向服务器（侦听器）发送一个 int，然后将 byte[] 转换为 int，然后服务器将计算“int num -2”并将其发送回客户端，后者将计算相同的结果，因此“num - 2" 直到 num 为 = 或 < 小于 0；

例子

1 run the server
2 run the client
3 digit 10
4 received back from server 8
5 client will subtract also 2 from 8 which now will be 6
6 send back 6 to server
7 server will subtract also 2 from 6 which now will be 4
8 send back 4 to client
9 client will subtract also 2 from 4 which now will be 2
10 client  send back 2 to server
11 server will subtract also 2 from 2 which now will be 0
12 client receive 0
13 when client receive num =0 or num < 0 (0 or negative) program shut down.

Answer 1

您可以简单地调用一个实用函数将字节数组转换为 int。

public static int byteArrayToInt(byte[] b) {
   return b[3] & 0xFF | (b[2] & 0xFF) << 8 | (b[1] & 0xFF) << 16 |(b[0] & 0xFF) << 24;
}

希望这会有所帮助。