UDPClient not receiving packets on HTC G2 - xamarin.android

Question

I'm attempting to receive a UDP Broadcast under Mono for Android and I am seeing no data coming in. This is somewhat perplexing because it works fine on the Galaxy Tab 7 and Galaxy Tab 10 (Android v 3.2) I have, but fails on an HTC G2 (Android v2.3.4).
The code is straightforward:
public void BeginDiscover()
{
var packet = new DiscoverPacket();
lock (m_syncRoot)
{
var localEndpoint = new IPEndPoint(m_local, 0);
using (var udp = new UdpClient(localEndpoint))
{
var remoteEndpoint = new IPEndPoint(IPAddress.Broadcast, DiscoverPort);
udp.Send(packet.Data, packet.Data.Length, remoteEndpoint);
Thread.Sleep(100);
}
}
}
I have verified that the manifest includes this line:
<uses-permission android:name="android.permission.INTERNET" />
Though this is happening in Debug, so that should be implicitly set anyway.
Other very strange observations:
Again, this is working just fine on another type of device
The handler listening for UDP broadcasts (which list listening for the response) does see this outbound packet. The code for this listener is also straightforward:
[listener code]
private void Start()
{
m_discoverListener = new UdpClient(DiscoverPort);
m_discoverListener.BeginReceive(DiscoverCallback, m_discoverListener);
}
private void DiscoverCallback(IAsyncResult result)
{
try
{
var ep = new IPEndPoint(IPAddress.Any, DiscoverPort);
var data = m_discoverListener.EndReceive(result, ref ep);
// filter out what we send
var add = AddressWithoutPort(ep.Address);
if (add == m_local.ToString()) return;
// parse discover response
// [clipped for clarity]
}
finally
{
m_discoverListener.BeginReceive(DiscoverCallback, m_discoverListener);
}
}
Wireshark running on a separate PC on the same network does see the discover request packet (from above)
The "discovered" device is also seeing it, because Wireshark is also seeing the reply
The Android device UDP listener is not receiving the response packet
The only major differences between devices that I can think of (other than different OEMs implementing the platform) is that the G2 has a cellular radio built in and the Galaxy Tab does not. In my specific test case, I have no SIM card in the phone, though, so no cellular connection is being made. Note that the code above is explicitly using the local endpoint that is on the WiFi network.
Is there a known issue with UDP on the G2 specifically or generally on older implementations of the Android platform?

Answer 1

It took a bit of work as the UDP response in question is coming from a microcontroller on the device and I wanted to make absolutely certain that it wasn't an issue on the micro end (though I suspected it wasn't). I created a PC-based simulator for the microcontroller device that handles my Android UDP request and that sends back the exact same UDP response that the microcontroller does, then verified all of the traffic looks fine with Wireshark.
The net result is that I see he exact same behavior with the simulator. The Galaxy Tab 7 and 10 devices receive the UDP response no problem. The HTC G2 never does. This leads me to conclude that one of the following is true:
a) The HTC G2 specifically has an implementation bug preventing it from receiving (or at least passing along) UDP broadcasts on the network
or
b) The older Android build has his bug.
Until I find different hardware with the same Android version as the G2 (v2.3) I can't tell which is the case. In either event, it's a bug that makes this (and potentially other) hardware unusable for my specific solution.

Answer 2

I have a couple of applications on the market based on UDP communication.
I have problems with HTC phones not receiving the UDP broadcast packets sent from another device... if sent from the same device, the packets arrive.
so, I think the problem is in HTC, and I found a possible solutions online (even though I have not tried it):
http://www.flattermann.net/2010/09/fix-udp-broadcasts-on-htc-phones-running-stock-firmware/