On an Android application which should work on Android 6+, I am trying to use network service discovery in order to check if some devices are available on my network.
Base on this part of the official documentation, I created this little POC:
class MainActivity : AppCompatActivity() {
companion object {
private const val TAG = "POC"
private const val SERVICE_TYPE = "_http._tcp."
}
private val serviceToResolve = mutableListOf<NsdServiceInfo>()
private var index = 0
public override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
findViewById<Button>(R.id.discover_btn).setOnClickListener {
search()
}
}
private fun search() {
lifecycleScope.launch(Dispatchers.IO) {
val serviceInfo = NsdServiceInfo().apply {
serviceName = "MyServiceTest"
serviceType = SERVICE_TYPE
port = 80
}
val registrationListener = object : NsdManager.RegistrationListener {
override fun onServiceRegistered(NsdServiceInfo: NsdServiceInfo) {}
override fun onRegistrationFailed(serviceInfo: NsdServiceInfo, errorCode: Int) {}
override fun onServiceUnregistered(arg0: NsdServiceInfo) {
}
override fun onUnregistrationFailed(serviceInfo: NsdServiceInfo, errorCode: Int) {}
}
val nsdManager = (getSystemService(Context.NSD_SERVICE) as NsdManager).apply {
registerService(serviceInfo, NsdManager.PROTOCOL_DNS_SD, registrationListener)
}
// Instantiate a new DiscoveryListener
val discoveryListener = object : NsdManager.DiscoveryListener {
override fun onDiscoveryStarted(regType: String) {
}
override fun onServiceFound(service: NsdServiceInfo) {
serviceToResolve.add(service)
}
override fun onServiceLost(service: NsdServiceInfo) {}
override fun onDiscoveryStopped(serviceType: String) {}
override fun onStartDiscoveryFailed(serviceType: String, errorCode: Int) {
nsdManager.stopServiceDiscovery(this)
}
override fun onStopDiscoveryFailed(serviceType: String, errorCode: Int) {
nsdManager.stopServiceDiscovery(this)
}
}
nsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, discoveryListener)
delay(5000)
resolveService(nsdManager)
}
}
private fun resolveService(nsdManager: NsdManager) {
if (serviceToResolve.size > index) {
nsdManager.resolveService(serviceToResolve[index], object : NsdManager.ResolveListener {
override fun onResolveFailed(serviceInfo: NsdServiceInfo?, errorCode: Int) {
index++
resolveService(nsdManager)
}
override fun onServiceResolved(serviceInfo: NsdServiceInfo?) {
Log.d(TAG, "onServiceResolved : $serviceInfo || ${serviceInfo?.attributes}")
index++
resolveService(nsdManager)
}
})
} else {
Log.d(TAG, "Nothing to resolve")
}
}
}
This code works correctly on from Android 7 to 11. But does not work correctly on Android 6. I can resolve correctly the services, but it does not contain any attributes according to the log :
Log.d(TAG, "onServiceResolved : $serviceInfo || ${serviceInfo?.attributes}")
For example, here the result on Android 6.0:
onServiceResolved : name: TJA470 (TJA470-F40103), type: ._http._tcp, host: /10.0.0.177, port: 80 || {}
And here the result on Android 11:
onServiceResolved : name: TJA470 (TJA470-F40103), type: ._http._tcp, host: /10.0.0.177, port: 80, txtRecord: 1device.type=urn:schemas-hager-com:device:tja470:1device.modelName=TJA470 export=Yes$device.modelURL=http://www.hager.comdevice.hostName=TJA470-F40103device.manufacturer=Hagerdevice.ip=10.0.0.1771device.modelDescription=Hager Pilot Configuration+device.manufacturerURL=http://www.hager.com(device.UDN=uuid:M2VSZEVUELAJYECHAJLU1708device.UPC=470,device.serialNumber=M2VSZEVUELAJYECHAJLU1708device.modelNumber=3.1.15'presentationURL=http://TJA470-F40103:80*device.friendlyName=TJA470 (TJA470-F40103) || {device.type=[117, 114, 110, 58, 115, 99, 104, 101, 109, 97, 115, 45, 104, 97, 103, 101, 114, 45, 99, 111, 109, 58, 100, 101, 118, 105, 99, 101, 58, 116, 106, 97, 52, 55, 48, 58, 49], device.modelName=[84, 74, 65, 52, 55, 48], export=[89, 101, 115], device.modelURL=[104, 116, 116, 112, 58, 47, 47, 119, 119, 119, 46, 104, 97, 103, 101, 114, 46, 99, 111, 109], device.hostName=[84, 74, 65, 52, 55, 48, 45, 70, 52, 48, 49, 48, 51], device.manufacturer=[72, 97, 103, 101, 114], device.ip=[49, 48, 46, 48, 46, 48, 46, 49, 55, 55], device.modelDescription=[72, 97, 103, 101, 114, 32, 80, 105, 108, 111, 116, 32, 67, 111, 110, 102, 105, 103, 117, 114, 97, 116, 105, 111, 110], device.manufacturerURL=[104, 116, 116, 112, 58, 47, 47, 119, 119, 119, 46, 104, 97, 103, 101, 114, 46, 99, 111, 109], device.UDN=[117, 117, 105, 100, 58, 77, 50, 86, 83, 90, 69, 86, 85, 69, 76, 65, 74, 89, 69, 67, 72, 65, 74, 76, 85, 49, 55, 48, 56], device.UPC=[52, 55, 48], device.serialNumber=[77, 50, 86, 83, 90, 69, 86, 85, 69, 76, 65, 74, 89, 69, 67, 72, 65, 74, 76, 85, 49, 55, 48, 56], device.modelNumber=[51, 46, 49, 46, 49, 53], presentationURL=[104, 116, 116, 112, 58, 47, 47, 84, 74, 65, 52, 55, 48, 45, 70, 52, 48, 49, 48, 51, 58, 56, 48], device.friendlyName=[84, 74, 65, 52, 55, 48, 32, 40, 84, 74, 65, 52, 55, 48, 45, 70, 52, 48, 49, 48, 51, 41]}
As you can see, the attributes are presents on Android 11 and not on Android 6.0. Is it an issue from the NSD_SERVICE on Android 6.0 or it is an issue of the POC I developped?
The NsdServiceInfo class has been added in API 16 ans the getAttributes method has been added in API 21. So normally everything should work correctly on Android 6.0 :(
The issue is not in my code but in the Android SDK according to this ticket.
On Android 5 and 6 I need to use a third party library like Jmdns.