07101994 / zeroconf

Bonjour support for .NET Core, .NET 4.5, Windows Phone 8, 8.1, Xamarin iOS and Android, and Windows Store apps

Zeroconf

Bonjour/mDNS discovery support for .NET v4.6.1, UWP, Xamarin & .NET Standard 2.0

The core logic is implemented primarily .NET Standard 2.0. Due to networking APIs being platform-specific on earlier platforms, a platform-specific version is required. Just make sure that you also install the NuGet to your main app and you'll be all set.

Installation

The easiest way to get started is to use the NuGet package.

Install-Package Zeroconf

Current Build Status:

Usage

There's are two methods with a few optional parameters:

using Zeroconf;
public async Task ProbeForNetworkPrinters()
{
    IReadOnlyList<IZeroconfHost> results = await
        ZeroconfResolver.ResolveAsync("_printer._tcp.local.");
}

public async Task EnumerateAllServicesFromAllHosts()
{
    ILookup<string, string> domains = await ZeroconfResolver.BrowseDomainsAsync();            
    var responses = await ZeroconfResolver.ResolveAsync(domains.Select(g => g.Key));            
    foreach (var resp in responses)
        Console.WriteLine(resp);
}

The ResolveAsync method has one required and several optional parameters. The method signature is as follows:

Task<IReadOnlyList<IZeroconfHost>> ResolveAsync(string protocol, TimeSpan scanTime = default(TimeSpan), int retries = 2, int retryDelayMilliseconds = 2000, Action<IZeroconfHost> callback = null, CancellationToken cancellationToken = default(CancellationToken));

The BrowseDomainsAsync method has the same set of optional parameters. The method signature is:

Task<ILookup<string, string>> BrowseDomainsAsync(TimeSpan scanTime = default (TimeSpan), int retryDelayMilliseconds = 2000, Action<string, string> callback = null, CancellationToken cancellationToken = default (CancellationToken))

What you get back from the Browse is a lookup, by service name, of a group that contains every host offering that service. Thst most common use would be in the example above, passing in all keys (services) to the Resolve method. Otherwise, you can also see what hosts are offering which services as well.

IObservable

Starting in v2.5, there are two additional methods that return IObservable's instead of Tasks. These methods are otherwise identical to the *Async versions but are more suitable for some usages.

Parameters

Parameter Name	Default Value	Notes
protocol		Service to query. Almost always must end with .local.
scanTime	2 seconds	Amount of time to listen for responses
retries	2	Number of times to attempt to bind to the socket. Binding may fail if another app is currently using it.
retryDelayMilliseconds	2000	Delay between retries
callback	null	If provided, called per IZeroconfigHost as they are processed. This can be used to stream data back prior to call completion.
cancellationToken	CancellationToken.None	Optional use of task cancellation

Notes

The ResolveAsync method is thread-safe, however all calls to it are serialized as only one can be in-progress at a time.

Xamarin.Android 4.x Linker bug

There is currently a bug on Xamarin.Android 4.x that incorrectly strips out internal Socket methods. This has been fixed for the Xamarin.Android 5.0 series. As a workaround on 4.x, entering System; in to the Ignore Assemblies field in the Project Options->Build->Android Build page will fix the problem.

Android

You must call the WifiManager.MulticastLock manager Aquire and Release before/after you call the Zeroconf methods. Previous versions (prior to 2.7 did this internally, now it requires the caller to do it).

Something like thisl

// Somewhere early
var wifi = (WifiManager)ApplicationContext.GetSystemService(Context.WifiService);
var mlock = wifi.CreateMulticastLock("Zeroconf lock");

---
// Later, before you call Zeroconf
try
{
  mlock.Acquire();

  // Call Zeroconf
  ZeroconfResolver....
}
finally
{
  mlock.Release();
}

You'll also need to specify the correct permsision like this:

[assembly: UsesPermission(Android.Manifest.Permission.ChangeWifiMulticastState)]

UWP

You'll need to have the following permissions on your manifest depending on what networks you're trying to scan:

• Private Networks (Client & Server)
• Internet (Client & Server)

Credits

This library was made possible through the efforts of the following projects:

• ZeroconfRT by Sergey Aldoukhov
• DNS.NET Resolver by Alphons van der Heijden