net-mdns

A simple Multicast Domain Name Service based on RFC 6762. Can be used
as both a client (sending queries) or a server (responding to queries).

A higher level DNS Service Discovery based on RFC 6763 that automatically responds to any query for the
service or service instance.

Features

Targets Framework 4.6.1, .NET Standard 1.4 and 2.0
Supports IPv6 and IPv4 platforms
CI on Circle (Debian GNU/Linux), Travis (Ubuntu Xenial and OSX) and AppVeyor (Windows Server 2016)
Detects new and/or removed network interfaces
Supports multicasting on multiple network interfaces
Supports reverse address mapping
Supports service subtypes (features)
Handles legacy unicast queries, see #61

Getting started

Published releases are available on NuGet. To install, run the following command in the Package Manager Console

PM> Install-Package Makaretu.Dns.Multicast

or using .NET CLI run the following command in the project folder

> dotnet add package Makaretu.Dns.Multicast

Usage Service Discovery

Advertising

Always broadcast the service (“foo”) running on local host with port 1024.

using Makaretu.Dns;
var service = new ServiceProfile("x", "_foo._tcp", 1024);
var sd = new ServiceDiscovery();
sd.Advertise(service);

See the example advertiser for a working program.

Discovery

Find all services running on the local link.

using Makaretu.Dns;
var sd = new ServiceDiscovery();
sd.ServiceDiscovered += (s, serviceName) => { // Do something };

Find all service instances running on the local link.

using Makaretu.Dns;
var sd = new ServiceDiscovery();
sd.ServiceInstanceDiscovered += (s, e) => { // Do something };

See the example browser for a working program.

Usage Multicast

Event Based Queries

Get all the Apple TVs. The query is sent when a network interface is discovered.
The AnsweredReceived callback contains any answer that is seen, not just the answer
to the specific query.

using Makaretu.Dns;
var mdns = new MulticastService();
mdns.NetworkInterfaceDiscovered += (s, e) => mdns.SendQuery("appletv.local");
mdns.AnswerReceived += (s, e) => { // do something with e.Message };
mdns.Start();

Async Queries

Get the first answer to Apple TVs. Wait 2 seconds for an answer.

using Makaretu.Dns;
var service = "appletv.local";
var query = new Message();
query.Questions.Add(new Question { Name = service, Type = DnsType.ANY });
var cancellation = new CancellationTokenSource(2000);
using (var mdns = new MulticastService())
{
    mdns.Start();
    var response = await mdns.ResolveAsync(query, cancellation.Token);
    // Do something
}

Broadcasting

Respond to a query for the service. Note that ServiceDiscovery.Advertise is much easier.

using Makaretu.Dns;
var service = "...";
var mdns = new MulticastService();
mdns.QueryReceived += (s, e) =>
{
    var msg = e.Message;
    if (msg.Questions.Any(q => q.Name == service))
    {
        var res = msg.CreateResponse();
        var addresses = MulticastService.GetIPAddresses()
            .Where(ip => ip.AddressFamily == AddressFamily.InterNetwork);
        foreach (var address in addresses)
        {
            res.Answers.Add(new ARecord
            {
                Name = service,
                Address = address
            });
        }
        mdns.SendAnswer(res);
    }
};
mdns.Start();

net-dns - DNS data model and Name Server with serializer for the wire and master file format
net-udns - client for unicast DNS, DNS over HTTPS (DOH) and DNS over TLS (DOT)

License

The package is licensed under the MIT license. Refer to the LICENSE file for more information.