Multicast on Android 2.2

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Has anyone gotten Multicast to work on Android 2.2, specifically JmDNS for Bonjour service detection. There are many questions & answers from the Android 1.5->2.0 timeframe, including on stackOverflow, that indicate varying levels of success, and a bug in the bug tracker that indicate it was fixed, and closed, for 2.2 (http://code.google.com/p/android/issues/detail?id=2323) . I've tried the "TuneControl" source code, but that worked on ~1.5 and has not been updated, and does not work for me on 2.2.

So, the questions... 1) Has anyone seen multicast work on 2.2, specifically JmDNS, and specifically for Bonjour service detection?

2) What is necessary in code to make this work?

I'm using the appropriate permissions:

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

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

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

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

I acquire the multicast lock:

WifiManager wifi = (WifiManager)getSystemService( Context.WIFI_SERVICE );
if(wifi != null)
{
    MulticastLock mcLock = wifi.createMulticastLock("mylock");
    mcLock.acquire();
...

And then try to start jmDNS to look for servers:

    mdns = JmDNS.create(addr, HOSTNAME);
    jmdns.addServiceListener(TOUCH_ABLE_TYPE, listener);
    jmdns.addServiceListener(DACP_TYPE, listener);
    ...

The listener never sees any services. I've verified using Wireshark that the request packets are sent, and that the server responds, but the response packet are never seen by the socket listener code in the jmDNS library.

So... am I missing something? Is this still a bug? Has ANYONE gotten anything even remotely like this to work???

3 Answers

I've been doing a bit of research into this, and I believe it is a problem with Android in general, and fixed in or around Android 2.3.7.

It's a bit too anecdotal, but here's what I tested:

  • HTC Desire, 2.2, stock: fail
  • HTC Desire, 2.3.7, CyanogenMod: success
  • Motorola Milestone, 2.1-update1: fail
  • HTC Desire S, 2.3.3: fail
  • Acer Iconia A501, 3.2.1: success
  • Samsung something, 2.3.3: fail
  • HTC Legend, 2.2 I think: fail

When I say 'fail', in fact they were all able to send multicast messages to the 'success' devices, but never receive anything back except their own messages - as jldupont describes.

Note that the multicast IM app Kouchat is only available for 2.3.7 onwards, even though it can be made to compile for as far back as 2.1, which gives further credence to this theory.

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