nsd

Description:

nsd

nsd #




A Flutter plugin for network service discovery and registration (aka NSD / DNS-SD / Bonjour / mDNS).

Basic Usage #
Service Discovery #
import 'package:nsd/nsd.dart';

final discovery = await startDiscovery('_http._tcp');
discovery.addListener(() {
// discovery.services contains discovered services
});

// ...

await stopDiscovery(discovery);
copied to clipboard
or alternatively:
discovery.addServiceListener((service, status) {
if (status == ServiceStatus.found) {
// put service in own collection, etc.
}
});
copied to clipboard
Service Registration #
import 'package:nsd/nsd.dart';

final registration = await register(
const Service(name: 'Foo', type: '_http._tcp', port: 56000));

// ...

await unregister(registration);
copied to clipboard

Permissions #
Android #
Add the following permissions to your manifest:
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
copied to clipboard
iOS #
Add the following permissions to your Info.plist (replace service type with your own):
<key>NSLocalNetworkUsageDescription</key>
<string>Required to discover local network devices</string>
<key>NSBonjourServices</key>
<array>
<string>_http._tcp</string>
</array>
copied to clipboard

Example application #

The plugin includes an example application that can be used to start multiple discoveries
and register multiple services. It will discover its own services but also other services of type
_http._tcp in the local network, such as the printer in the screenshot above.

Use the action button to add a discovery or register a new service.
Swipe the cards left or right to dismiss a discovery or service.
The application log will show the calls and callbacks platform side vs. native side.
The source code demonstrates how to use the discovery object as a
ChangeNotifier.


Minimum OS Requirements #

Android: API level 21 (Android 5.0)
iOS: 12.0
macOS: 10.11 (El Capitan)
Windows 10 (19H1/1903) (Mai 2019 Update)


Advanced Usage #
Get IP Addresses for Service #
First, do you really need the IP address? If you just want to connect to the service,
the host name that is supplied with the service should do just fine. In fact, connecting by
host name is recommended on the Apple Developer Forums.
If you do need the IP address, you can configure automatic ip lookup for your discovery
like this:
final discovery = await startDiscovery(serviceType, ipLookupType: IpLookupType.any);
copied to clipboard
Each discovered service will now have a list of IP addresses attached to it.
Discover All Services of All Types on Local Network #
The current way to do this would be:

Start discovery using special service type _services._dns-sd._udp
Receive list of all service types in network
Do discovery for each service type

Start the discovery like this:
final discovery = await startDiscovery('_services._dns-sd._udp', autoResolve: false);
copied to clipboard
The autoResolve flag is important because the results are not real services and cannot be resolved. The discovery.services list will then be populated with the answers.
The Service instances returned will contain service type info, like so:
{service.type: _tcp.local, service.name: _foo, ...}
{service.type: _tcp.local, service.name: _bar, ...}
copied to clipboard
The first component of the service type (e.g. _foo) is contained in the service name attribute,
the second component of the service type (e.g. _tcp) is contained in the service type attribute.
Even though using a service structure to represent a service type feels like a hack, it seems to be
consistent on Android / macOS / iOS platform APIs. Since they are all doing it,
the plugin has the same behavior.
Note: this currently doesn't function 100% on Windows platforms. While it will detect the types of
services registered by other machines correctly, it will not detect types of services that were
registered using the plugin.
Disable service name validation #
Service names are validated by the plugin according to RFC 6335:

MUST be at least 1 character and no more than 15 characters long
MUST contain only US-ASCII [ANSI.X3.4-1986] letters 'A' - 'Z' and 'a' - 'z', digits '0' - '9', and hyphens ('-', ASCII 0x2D or decimal 45)
MUST contain at least one letter ('A' - 'Z' or 'a' - 'z')
MUST NOT begin or end with a hyphen
hyphens MUST NOT be adjacent to other hyphens

If you are getting the error message "Service type must be in format..." but you still want to work
with service names that do not conform to the rules, you can disable service name validation entirely:
disableServiceTypeValidation(true);
copied to clipboard
Be aware that some network environments might not support non-conformant service names.
Enable Debug Logging #
In order to help debugging, logging can be enabled for individual topics. For example
enableLogging(LogTopic.errors);
enableLogging(LogTopic.calls);
copied to clipboard
will log errors and all calls to the native side (and their callbacks), which often yields useful information.

Contributors #
lxp-git - wrote the Windows prototype!

Projects using nsd #
🎮 Tic Tac Toe Local Multiplayer Game for Android by Laks Castro