android resolve .local (mDNS)

Question

I'm looking for a solution to resolve .local host names with Android 4.0.4 (no NSD, due to API level 15). On the device I don't have any service to discover, just the hostname. Could you please provide an example how to resolve? I integrated the jmDNS, but don't know how to use for host name resolving.

win-cmd:

ping kcmeasurement.local

Pinging kcmeasurement.local [10.202.0.29] with 32 bytes of data:
Reply from 10.202.0.29: bytes=32 time<1ms TTL=64
...

Thank you,

Daniel

Ezraezri

This is a shortcoming of Android. If you want it fixed in the OS, please drop by and star (upvote) this android buganizer issue. – Ingraham

Answer 1

I had almost the same requirements as your question, apart from the requirement to use jmDNS, so I solved it with NSD. I realize this doesn't address your question exactly, but thought it might still be somewhat helpful for yourself and others to see how I solved it.

I setup an NSD discovery listener and an NSD resolve listener, and within the discovery listener code, added a filter for the target host name (e.g. "kcmeasurement", or in my case, "garagedoor").

There is a blog post here which explains in detail how to do that. Refer to steps 3-4, which are dealing with the Android App code required.

http://www.dodgycoder.net/2015/02/setting-up-bonjourzeroconfmdnsnsd.html

For your case, I would imagine you would have to do the equivalent process but just using the jmDNS library instead of NSD.

Flaky

This appears to be about resolving an mDNS service rather than resolving a name - in particular, the writeup proposes changing the configuration of the raspberry pi, rather than merely recognizing the rapsberrypi.local mDNS name it should already have out of the box. – Nan

I just managed to reach RPi from PC, - only after I installed samba and restarted avahi-daemon. No luck from Android – Judgment

the issue with android is that it doesn't ship with an mdns service. .local addresses are handled by avahi in Linux and bonjour in ios/macos. jmdns or the nsd app should enable that – Mallen

Answer 2

You should be able to use the InetAddress class to resolve the hostname for a given IP address. For example, using the IP address provided in the original question, try the following:

try
{
    String hostname = InetAddress.getByName("10.202.0.29").getHostName();
}
catch (UnknownHostException e)
{
    Log.e("MyApplication", "Attempt to resolve host name failed");
}

Since this is a network operation, make sure that it is not performed on the UI thread.

EDIT

You should be able to resolve a local hostname with jmDNS as follows:

InetAddress localHost = InetAddress.getByName("10.202.0.29");
JmDNS jmdns = JmDNS.create(localHost);
String localHostName = jmdns.getHostName();

Harass

Thank you for your reply! Unfortunately It's not working, because the "kcmeasurement" is an mDNS host name and my android version (4.0.4) doesn't have a built-in mDNS resolver. So if I call the InetAddress.getByName I got a not found exception. – Ezraezri

Moreover I included the jmDNS package into my Apk, so the advertising works, but I don't find how to resolve .local names. – Ezraezri

-1 Neither the original nor amended form of this answer address the actual question at all. It's likely that you did not understand what was being asked - the so called local "name" you claim to be resolving in the second part is neither an mDNS name nor any sort of name at all, it's a numeric IP address, and there's no need to "resolve" that at all. – Nan

I am just using the IP address to create a 'InetAddress' object. The host name is found by calling 'getHostName'. – Harass

That's not what was asked. The question is about turning a name like "kcmeasurement.local" into an IP address. Once you have a numeric IP address, you're done. You started with a numeric IP address, which makes your response completely inapplicable to the problem of the question asked - you're assuming prior knowledge of the very thing the question is about discovering! – Nan