Question

我试图传达两个java程序，没问题。程序A发送带有＆＃34;令牌＆＃34;的消息。和程序B接收消息并打印出来。我遇到的问题是我想在消息长度发送到程序B之前创建具有准确长度的数组，但我不知道我该怎么做。

public class ProgramA {
public static void main(String[] args) {
    try {
        DatagramSocket datagramSocket = new DatagramSocket();
        String message = "token";
        InetAddress addr = InetAddress.getByName("localhost");
        DatagramPacket datagram = new DatagramPacket(message.getBytes(),message.getBytes().length, addr, 5556);
        datagramSocket.send(datagram);
        datagramSocket.close();
    }
    catch (IOException e) {
        e.printStackTrace();
    }
}

public class ProgramB {
public static void main(String[] args) {
    try {
        InetSocketAddress addr = new InetSocketAddress("localhost", 5556);
        DatagramSocket datagramSocket = new DatagramSocket(addr);
        byte[] message = new byte[5];
        DatagramPacket datagram = new DatagramPacket(message, message.length);
        datagramSocket.receive(datagram);
        datagramSocket.close();
        for(int i = 0; i < message.length; i++) {
            System.out.print((char)message[i]);
        }
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
}

Answer 1

如果您知道消息的长度是最大X字节，则可以使用以下内容：

package experiment;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class ProgramA {
    public static void main(String[] args) {
        try {
            System.out.println("Started");
            DatagramSocket datagramSocket = new DatagramSocket();
            String message = "tokenasdfasdfasdfasdf";
            InetAddress addr = InetAddress.getByName("localhost");
            DatagramPacket datagramLength = new DatagramPacket(new byte[]{(byte)message.length()}, 1, addr, 5556);
            DatagramPacket datagram = new DatagramPacket(message.getBytes(),message.getBytes().length, addr, 5556);
            datagramSocket.send(datagramLength);
            datagramSocket.send(datagram);
            datagramSocket.close();
            System.out.println("Done");
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

package experiment;

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

public class ProgramB {
    public static void main(String[] args) {
        try {
            InetSocketAddress addr = new InetSocketAddress("localhost",     5556);
            DatagramSocket datagramSocket = new DatagramSocket(addr);
            byte[] messageLength = new byte[1];
            DatagramPacket datagramLength = new DatagramPacket(messageLength, 1);
            datagramSocket.receive(datagramLength);
            byte[] message = new byte[(int)messageLength[0]];
            DatagramPacket datagram = new DatagramPacket(message, message.length);
            datagramSocket.receive(datagram);
            datagramSocket.close();
            for(int i = 0; i < message.length; i++) {
                System.out.print((char)message[i]);
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

这项工作假设消息的长度不超过127;否则，带有消息长度的datagramPacket必须包含多个字节

Java程序与DatagramSocket

1 个答案: