Question

我需要使用android设备在wifi网络中“查找”特定设备。设备正在端口7432上侦听，我需要以字节为单位发送02904并获得IP地址响应。设备数量可能从0到n。我需要每个设备上的IP地址（来自响应或发现）到目前为止，这是我的代码（我并不是说它对我有用）：

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.logging.Level;
import java.util.logging.Logger;

public class DiscoveryThread implements Runnable {
    @Override
    public void run() {
        try {
            //Keep a socket open to listen to all the UDP trafic that is destined for this port
            DatagramSocket socket = new DatagramSocket(7432, InetAddress.getByName("255.255.255.255"));
            socket.setBroadcast(true);

            do {
                System.out.println(getClass().getName() + ">>>Ready to receive broadcast packets!");

                //Receive a packet
                byte[] recvBuf = new byte[5];
                DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
                socket.receive(packet);

                //Packet received
                System.out.println(getClass().getName() + ">>>Discovery packet received from: " + packet.getAddress().getHostAddress());
                System.out.println(getClass().getName() + ">>>Packet received; data: " + new String(packet.getData()));

                //See if the packet holds the right command (message)
                String message = new String(packet.getData()).trim();
                if (message.equals("DISCOVER_FUIFSERVER_REQUEST")) {
                    byte[] sendData = "DISCOVER_FUIFSERVER_RESPONSE".getBytes();

                    //Send a response
                    DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, packet.getAddress(), packet.getPort());
                    socket.send(sendPacket);

                    System.out.println(getClass().getName() + ">>>Sent packet to: " + sendPacket.getAddress().getHostAddress());
                }
            } while (true);
        } catch (IOException ex) {
            Logger.getLogger(DiscoveryThread.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    static DiscoveryThread getInstance() {
        return DiscoveryThreadHolder.INSTANCE;
    }

    private static class DiscoveryThreadHolder {

        private static final DiscoveryThread INSTANCE = new DiscoveryThread();
    }

}

我尝试过：

Android send udp broadcast silently fails

https://lab.dyne.org/AndroidUDPBroadcast

http://rocknirmana.blogspot.com/2013/08/sending-udp-broadcast-socket-messages.html

https://jackiexie.com/2015/07/15/network-discovery-using-udp-broadcast-java/

https://developer.android.com/reference/java/net/DatagramSocket

http://www.helloandroid.com/tutorials/simple-udp-communication-example

https://www.baeldung.com/java-broadcast-multicast

https://answers.unity.com/questions/250732/android-build-is-not-receiving-udp-broadcasts.html

https://pzoleeblogen.wordpress.com/2014/03/04/android-udp-broadcast-message-is-not-received/

清单：

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>

在我链接的大多数示例中，我得到的响应是“ 192.168.0.230”，并且我需要一个IP列表，例如["192.168.0.101", "192.168.0.102", "192.168.0.103"]（这是它们在我的网络上的外观，我看到了它们在具有这些IP的路由器中，我只是无法在我的应用中获取它们）。我对网络不太熟悉，也许我是用错误的方式开始的，但是我变得绝望了。

无法使用Android UDP广播在本地WiFi网络上发现设备

0 个答案: