Android Implementations

Android Implementations

On Android you choose the backend per call with implType:

	NSD (default)	DNSSD
Engine	Android's NsdManager	mDNSResponder embedded in the library
Depends on	The system NSD service, varies by device	Only the library's native code
mDNS host name in host	🟡	✅
All addresses	🟡	✅
TXT order kept when publishing	🟡	✅
Updates re-emitted as resolved	🟡	❌
Concurrent resolves	🟡	✅
Error domain	'NsdManager'	'DNSSD'

The embedded mDNSResponder comes from Discord's RxDNSSD fork.

import Zeroconf, { ImplType } from 'react-native-zeroconf'

zeroconf.scan({ type: 'http', implType: ImplType.DNSSD })
zeroconf.publishService({ type: 'http', protocol: 'tcp', name: 'MyServer', port: 8080, implType: ImplType.DNSSD })

On iOS, macOS and tvOS implType is ignored.

Which one should I use?

Start with NSD if you target recent Android versions and it finds your devices.

Switch to DNSSD when:

• NSD finds nothing, or stops finding services after a few scans (common on some OEM builds),
• you need the host name on Android versions before 16,
• you publish TXT records whose order matters,
• you discover printers (pdl-datastream, ipp) and NSD misses them.

Native code in the library is built with 16 KB page alignment, which Google Play requires for apps targeting Android 15+.

Rules of thumb

• One scan per instance. Calling scan() with a different implType on the same instance moves that instance's scan to the other implementation. Separate instances can scan at the same time, and NSD and DNSSD scans can run concurrently.
• stop() without arguments stops the implementation the instance's last scan() used.
• unpublishService(name) without implType uses the implementation the service was published with.
• After stop(), give DNSSD a short delay (around 500 ms) before scanning again.

Known NSD reliability issues

These are platform issues that affect every mDNS library using NsdManager:

• discovery silently stops after a while, after screen lock or when backgrounded,
• a service is found but its resolve fails,
• multicast is throttled by battery optimizations on some manufacturers (Samsung, Xiaomi, Huawei...),
• network changes (Wi-Fi reconnect, band switch, mesh handoff, VPN) break discovery.

Workarounds: use DNSSD, stop the scan when the app goes to the background and scan again when it becomes active, and retry a scan that returned nothing. See Troubleshooting and FAQ.

References

• NsdManager
• RxDNSSD (Discord fork)