DatagramSocket.recieve() never recieves UDP packet-CodePudding

I have the below code to wait and listen for a UDP broadcast sent from a server. However at socket.recieve(packet) it waits and the UDP packet never arrives. It is definitely being sent from the server. Stepping through the code everything appears to be correct, where am I going wrong?

public class BroadcastListenerService extends Service {
    static String UDP_BROADCAST = "UDPBroadcast";
DatagramSocket socket;


private void listenAndWait(Integer port) throws Exception {
    byte[] recvBuf = new byte[1000];

    if (socket == null || socket.isClosed()) {
        socket = new DatagramSocket(port); // Can receive broadcasts
       
        socket.setBroadcast(true);
        socket.setReuseAddress(true);
        Logger.doLog(LogDetail.Debug,"Broadcast? "   socket.getBroadcast());
        Logger.doLog(LogDetail.Debug,"ReuseAddr: "   socket.getReuseAddress());
        Logger.doLog(LogDetail.Debug,"Local Addr: "   socket.getLocalAddress().toString());
        Logger.doLog(LogDetail.Debug,"Local Port: "   socket.getLocalPort());

    }
    DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
    socket.receive(packet);

A potential issue is the socket cannot access the local INetaddress? The return value of socket.getLocalAddress is: ::/::

The code for the server side sends the UDP broadcast as follows:

Public Sub SendBroadcast(port As Integer, msg As String)

    Try
        Dim sock As New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)
        sock.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1)
        Dim addr As IPAddress = bcAddress 
        Dim buff As Byte() = Encoding.ASCII.GetBytes(msg)
        Dim ep As New IPEndPoint(addr, port)
        sock.SendTo(buff, ep)
    Catch ex As Exception
        Debug.WriteLine("Exception sending broadcast: " & ex.ToString)
    End Try
End Sub

All variable values appear to have the information that I would expect to see, correct port numbers, addresses and so on.

CodePudding user response：

It appears the issue was something to do with the local network. Once the network was changed the UDP packets began to come through.