Android手机创建热点并发送UDP广播的时候出了问题

Question

在做一个Android程序，需要监听局域网中的UDP广播，并且发送UDP广播。当两部手机同时连到一个路由器的时候就能正常接收发送UDP广播，但是当用其中一部手机建立wifi热点，另一部手机连这个wifi热点的时候，建立wifi热点的手机发送广播就会出现这样的错误：sendto failed: ENETUNREACH (Network is unreachable)
请问这是为什么？

附上UDP广播部分的代码：

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

public class UdpHelper {
private int port = 9888;
private DatagramSocket ds = null;
private DatagramPacket dp = null;
private byte[] buf = new byte[1024]; //存储发来的消息
private StringBuffer sbuf ;

public UdpHelper() {
    sbuf = new StringBuffer();
    try {
        ds = new DatagramSocket(port);
    } catch (SocketException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    dp = new DatagramPacket(buf, buf.length);
}


public String SendMessage(String msg) {
    String host = "255.255.255.255";        //广播地址
    String message = msg;

    try {
        InetAddress adds = InetAddress.getByName(host);
        DatagramSocket ds = new DatagramSocket();
        DatagramPacket dp = new DatagramPacket(message.getBytes(),
                message.length(), adds, port);
        ds.send(dp);
        ds.close();
    } catch (UnknownHostException e) {
        return e.getMessage();
    } catch (SocketException e) {
        return e.getMessage();
    } catch (IOException e) {
        return e.getMessage();
    }
    return "Success";
}

public String ReceiveMessage()
{
    sbuf.delete(0, sbuf.length());
    try {
        ds.receive(dp);
        int i;
        for(i=0;i<1024;i++){
            if(buf[i] == 0){
                break;
            }
            sbuf.append((char) buf[i]);
        }
        buf = new byte[1024];
        dp = new DatagramPacket(buf, buf.length);
    } catch (IOException e) {
        return e.getMessage();
    }
    return sbuf.toString();
}

}

Answer 1

https://zhidao.baidu.com/question/556117881.html