java中如何通过UDP发送int

Question

我正在尝试编写一些通过 UDP 发送单个 int 的代码。到目前为止我的代码：

发送者：

int num = 2;

DatagramSocket socket = new DatagramSocket();
ByteArrayOutputStream bout = new ByteArrayOutputStream();
PrintStream pout = new PrintStream( bout );
pout.print(num);
byte[] barray = bout.toByteArray();
DatagramPacket packet = new DatagramPacket( barray, barray.length );
InetAddress remote_addr = InetAddress.getByName("localhost");           
packet.setAddress( remote_addr );
packet.setPort(1989);
socket.send( packet );

接收者：

        DatagramSocket socket = new DatagramSocket(1989);
        DatagramPacket packet = new DatagramPacket(new byte[256] , 256);

        socket.receive(packet);

        ByteArrayInputStream bin = new ByteArrayInputStream(packet.getData());

        for (int i=0; i< packet.getLength(); i++)
        {
        int data = bin.read();
        if(data == -1)
        break;
        else
        System.out.print((int) data);

问题是接收者在屏幕上打印“50”，这显然是不正确的。我认为问题可能是我以某种方式将它作为字符串或其他东西发送，但它读取不正确。有什么帮助吗？

Answer 1

使用数据流，例如：

import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        final ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
        final DataOutputStream dataOut = new DataOutputStream(byteOut);
        dataOut.writeInt(1);
        dataOut.writeDouble(1.2);
        dataOut.writeLong(4l);
        dataOut.close(); // or dataOut.flush()
        final byte[] bytes = byteOut.toByteArray();
        final ByteArrayInputStream byteIn = new ByteArrayInputStream(bytes);
        final DataInputStream dataIn = new DataInputStream(byteIn);
        final int integ = dataIn.readInt();
        final double doub = dataIn.readDouble();
        final long lon = dataIn.readLong();
        System.out.println(integ);
        System.out.println(doub);
        System.out.println(lon);
    }

}

Answer 2

InputStream.read() 返回单个字节，而不是 32 位整数（请参阅 javadoc）。所以你想要的是

ObjectInputStream os = new ObjectInputStream(bin);
os.readInt();

Answer 3

问题是您收到的是“2”的字符代码，而不是实际的 2 作为整数。尝试将您的接收器代码更改为：

    DatagramSocket socket = new DatagramSocket(1989);
    DatagramPacket packet = new DatagramPacket(new byte[256] , 256);

    socket.receive(packet);

    System.out.print(new String(packet.getData()));

但我猜 ObjectInputStream 解决方案更适合您。