docs: respond to a query

README.md

@@ -24,6 +24,8 @@ Published releases are available on [NuGet](https://www.nuget.org/packages/Makar
 
 ## Usage
 
+### Discovery
+
 Get all the Apple TVs. The query is sent when a network interface is discovered.
 
 ```csharp
@@ -35,6 +37,37 @@ mdns.AnswerReceived += (s, e) => { // do something with e.Message };
 mdns.Start();
 ```
 
+### Broadcasting
+
+Respond to a query for the service.
+
+```csharp
+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();
+```
+
 # License
 Copyright © 2018 Richard Schneider (makaretu@gmail.com)
 

test/MulticastServiceTest.cs

@@ -5,6 +5,7 @@
 using System.Linq;
 using System.Net;
 using System.Net.NetworkInformation;
+using System.Net.Sockets;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -256,11 +257,16 @@ public void Multiple_Services()
                 if (msg.Questions.Any(q => q.Name == service))
                 {
                     var res = msg.CreateResponse();
-                    res.Answers.Add(new ARecord
+                    var addresses = MulticastService.GetIPAddresses()
+                        .Where(ip => ip.AddressFamily == AddressFamily.InterNetwork);
+                    foreach (var address in addresses)
                     {
-                        Name = service,
-                        Address = IPAddress.Parse("127.1.1.1")
-                    });
+                        res.Answers.Add(new ARecord
+                        {
+                            Name = service,
+                            Address = address
+                        });
+                    }
                     a.SendAnswer(res);
                 }
             };
@@ -285,8 +291,7 @@ public void Multiple_Services()
                 Assert.IsTrue(response.IsResponse);
                 Assert.AreEqual(MessageStatus.NoError, response.Status);
                 Assert.IsTrue(response.AA);
-                var answer = (ARecord)response.Answers[0];
-                Assert.AreEqual(IPAddress.Parse("127.1.1.1"), answer.Address);
+                Assert.AreNotEqual(0, response.Answers.Count);
             }
             finally
             {