From eff5b300b4a440b353c44b37ef1c928d96137e36 Mon Sep 17 00:00:00 2001
From: Richard Schneider <makaretu@gmail.com>
Date: Sat, 8 Jun 2019 16:17:56 +1200
Subject: [PATCH] feat(MessageEventArgs): detect legacy unicast messages

---
 Spike/Program.cs             | 3 ++-
 src/MessageEventArgs.cs      | 8 ++++++++
 src/MulticastClient.cs       | 9 ++++++++-
 test/MulticastServiceTest.cs | 8 ++++++--
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/Spike/Program.cs b/Spike/Program.cs
index 219c1d4..05804c3 100644
--- a/Spike/Program.cs
+++ b/Spike/Program.cs
@@ -51,13 +51,14 @@ static void Main(string[] args)
                 }
             };
 
+#if false
             var sd = new ServiceDiscovery(mdns);
             sd.Advertise(new ServiceProfile("x1", "_xservice._tcp", 5011));
             sd.Advertise(new ServiceProfile("x2", "_xservice._tcp", 666));
             var z1 = new ServiceProfile("z1", "_zservice._udp", 5012);
             z1.AddProperty("foo", "bar");
             sd.Advertise(z1);
-
+#endif
             mdns.Start();
             Console.ReadKey();
         }
diff --git a/src/MessageEventArgs.cs b/src/MessageEventArgs.cs
index 9aaba5c..c9e5c54 100644
--- a/src/MessageEventArgs.cs
+++ b/src/MessageEventArgs.cs
@@ -24,6 +24,14 @@ public class MessageEventArgs : EventArgs
         ///   The endpoint from the message was received.
         /// </value>
         public IPEndPoint RemoteEndPoint { get; set; }
+
+        /// <summary>
+        ///   Determines if the sender is using legacy unicast DNS.
+        /// </summary>
+        /// <value>
+        ///   <b>false</b> if the sender is using port 5353.
+        /// </value>
+        public bool IsLegacyUnicast => RemoteEndPoint.Port != MulticastClient.MulticastPort;
     }
 }
 
diff --git a/src/MulticastClient.cs b/src/MulticastClient.cs
index 5856232..4af58ac 100644
--- a/src/MulticastClient.cs
+++ b/src/MulticastClient.cs
@@ -19,7 +19,14 @@ class MulticastClient : IDisposable
     {
         static readonly ILog log = LogManager.GetLogger(typeof(MulticastClient));
 
-        const int MulticastPort = 5353;
+        /// <summary>
+        ///   The port number assigned to Multicast DNS.
+        /// </summary>
+        /// <value>
+        ///   Port number 5353.
+        /// </value>
+        public static readonly int MulticastPort = 5353;
+
         static readonly IPAddress MulticastAddressIp4 = IPAddress.Parse("224.0.0.251");
         static readonly IPAddress MulticastAddressIp6 = IPAddress.Parse("FF02::FB");
         static readonly IPEndPoint MdnsEndpointIp6 = new IPEndPoint(MulticastAddressIp6, MulticastPort);
diff --git a/test/MulticastServiceTest.cs b/test/MulticastServiceTest.cs
index 254c77e..4560f13 100644
--- a/test/MulticastServiceTest.cs
+++ b/test/MulticastServiceTest.cs
@@ -40,8 +40,12 @@ public void SendQuery()
             mdns.NetworkInterfaceDiscovered += (s, e) => ready.Set();
             mdns.QueryReceived += (s, e) =>
             {
-                msg = e.Message;
-                done.Set();
+                if ("some-service.local" == e.Message.Questions.First().Name)
+                {
+                    msg = e.Message;
+                    Assert.IsFalse(e.IsLegacyUnicast);
+                    done.Set();
+                }
             };
             try
             {