diff --git a/Knx.sln.DotSettings b/Knx.sln.DotSettings
index 4f9ff32..774accb 100644
--- a/Knx.sln.DotSettings
+++ b/Knx.sln.DotSettings
@@ -1,2 +1,3 @@
 <wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
-	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/Abbreviations/=IP/@EntryIndexedValue">IP</s:String></wpf:ResourceDictionary>
\ No newline at end of file
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/Abbreviations/=IP/@EntryIndexedValue">IP</s:String>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=Hpai/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
\ No newline at end of file
diff --git a/Knx/ExtendedMessageInterface/KnxMessage.cs b/Knx/ExtendedMessageInterface/KnxMessage.cs
index 1ad4cab..4f9c480 100644
--- a/Knx/ExtendedMessageInterface/KnxMessage.cs
+++ b/Knx/ExtendedMessageInterface/KnxMessage.cs
@@ -78,13 +78,13 @@ public bool IsPositiveConfirmation
     ///     Gets or sets the source (device-) address.
     /// </summary>
     /// <value>The source address.</value>
-    public KnxDeviceAddress? SourceAddress { get; set; } = "0/0/0";
+    public KnxDeviceAddress SourceAddress { get; set; } = "0/0/0";
 
     /// <summary>
     ///     Gets or sets the destination address (device or individual/logical address).
     /// </summary>
     /// <value>The destination address.</value>
-    public KnxAddress? DestinationAddress { get; set; }
+    public KnxAddress DestinationAddress { get; set; } = (KnxLogicalAddress)"0/0/0";
 
     /// <summary>
     ///     Gets the hop count, a message did, till it was received.
@@ -255,4 +255,4 @@ public static KnxMessage Deserialize(byte[] bytes)
             MessageType = msgType
         };
     }
-}
\ No newline at end of file
+}
diff --git a/Knx/KnxNetIp/IKnxNetIpClient.cs b/Knx/KnxNetIp/IKnxNetIpClient.cs
index ec6d848..4f33197 100644
--- a/Knx/KnxNetIp/IKnxNetIpClient.cs
+++ b/Knx/KnxNetIp/IKnxNetIpClient.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Reactive.Subjects;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -7,8 +6,8 @@ namespace Knx.KnxNetIp;
 
 public interface IKnxNetIpClient :
     IAsyncDisposable,
-    ISubject<KnxNetIpMessage>,
-    ISubject<IKnxMessage>
+    IObservable<KnxNetIpMessage>,
+    IObservable<IKnxMessage>
 {
     Task ConnectAsync();
 
diff --git a/Knx/KnxNetIp/KnxNetIpRoutingClient.cs b/Knx/KnxNetIp/KnxNetIpRoutingClient.cs
index 3d192ad..b4fe661 100644
--- a/Knx/KnxNetIp/KnxNetIpRoutingClient.cs
+++ b/Knx/KnxNetIp/KnxNetIpRoutingClient.cs
@@ -14,7 +14,7 @@ namespace Knx.KnxNetIp;
 /// <summary>
 ///     Used to connect to the Knx Bus via KnxNetIpRouting protocol.
 /// </summary>
-public sealed class KnxNetIpRoutingClient : IKnxNetIpClient
+public sealed class KnxNetIpRoutingClient : IKnxNetIpClient, IObservable<KnxHpai>
 {
     private readonly KnxDeviceAddress _deviceAddress;
     private readonly IPEndPoint _localEndpoint;
@@ -22,8 +22,10 @@ public sealed class KnxNetIpRoutingClient : IKnxNetIpClient
     private readonly CancellationTokenSource _receivingMessagesCancellationTokenSource;
     private readonly IPEndPoint _remoteEndPoint;
     private UdpClient? _udpClient;
+
     private readonly Subject<KnxNetIpMessage> _knxNetIpMessageSubject;
     private readonly Subject<IKnxMessage> _knxMessageSubject;
+    private readonly Subject<KnxHpai> _knxHpaiSubject;
 
     /// <summary>
     ///     Creates a new instance of the <see cref="KnxNetIpRoutingClient" /> class.
@@ -48,6 +50,7 @@ public KnxNetIpRoutingClient(
 
         _knxNetIpMessageSubject = new Subject<KnxNetIpMessage>();
         _knxMessageSubject = new Subject<IKnxMessage>();
+        _knxHpaiSubject = new Subject<KnxHpai>();
     }
 
     public async ValueTask DisposeAsync()
@@ -97,15 +100,14 @@ public async Task ConnectAsync()
         await Task.CompletedTask;
     }
 
-    IDisposable IObservable<KnxNetIpMessage>.Subscribe(IObserver<KnxNetIpMessage> observer)
-    {
-        throw new NotImplementedException();
-    }
+    IDisposable IObservable<KnxNetIpMessage>.Subscribe(IObserver<KnxNetIpMessage> observer) =>
+        _knxNetIpMessageSubject.Subscribe(observer);
 
-    IDisposable IObservable<IKnxMessage>.Subscribe(IObserver<IKnxMessage> observer)
-    {
-        throw new NotImplementedException();
-    }
+    IDisposable IObservable<IKnxMessage>.Subscribe(IObserver<IKnxMessage> observer) =>
+        _knxMessageSubject.Subscribe(observer);
+
+    IDisposable IObservable<KnxHpai>.Subscribe(IObserver<KnxHpai> observer) =>
+        _knxHpaiSubject.Subscribe(observer);
 
     ~KnxNetIpRoutingClient()
     {
@@ -122,6 +124,7 @@ private ValueTask Dispose(bool disposing)
 
             _knxNetIpMessageSubject.Dispose();
             _knxMessageSubject.Dispose();
+            _knxHpaiSubject.Dispose();
         }
 
         return ValueTask.CompletedTask;
@@ -230,24 +233,9 @@ private void InvokeKnxMessageReceived(IKnxMessage knxMessage)
         _knxMessageSubject.OnNext(knxMessage);
     }
 
-    private void InvokeKnxDeviceDiscovered(KnxHpai hostProtocolAddressInformation) =>
+    private void InvokeKnxDeviceDiscovered(KnxHpai hostProtocolAddressInformation)
+    {
         KnxDeviceDiscovered?.Invoke(this, hostProtocolAddressInformation);
-
-    void IObserver<KnxNetIpMessage>.OnCompleted() =>
-        _knxNetIpMessageSubject.OnCompleted();
-
-    void IObserver<IKnxMessage>.OnError(Exception error) =>
-        _knxMessageSubject.OnError(error);
-
-    void IObserver<IKnxMessage>.OnNext(IKnxMessage value) =>
-        _knxMessageSubject.OnNext(value);
-
-    void IObserver<IKnxMessage>.OnCompleted() =>
-        _knxMessageSubject.OnCompleted();
-
-    void IObserver<KnxNetIpMessage>.OnError(Exception error) =>
-        _knxNetIpMessageSubject.OnError(error);
-
-    void IObserver<KnxNetIpMessage>.OnNext(KnxNetIpMessage value) =>
-        _knxNetIpMessageSubject.OnNext(value);
+        _knxHpaiSubject.OnNext(hostProtocolAddressInformation);
+    }
 }
diff --git a/Knx/KnxNetIp/KnxNetIpTunnelingClient.cs b/Knx/KnxNetIp/KnxNetIpTunnelingClient.cs
index 2b9707d..af30746 100644
--- a/Knx/KnxNetIp/KnxNetIpTunnelingClient.cs
+++ b/Knx/KnxNetIp/KnxNetIpTunnelingClient.cs
@@ -273,7 +273,8 @@ private void OnKnxNetIpMessageReceived(KnxNetIpMessage message)
         }
 
         KnxNetIpMessageReceived?.Invoke(this, message);
-        ((ISubject<KnxNetIpMessage>)this).OnNext(message);
+
+        _knxNetIpMessageSubject.OnNext(message);
     }
 
     private async Task DisposeAsync(bool disposing)
@@ -512,22 +513,4 @@ private void SetSequenceCount(TunnelingMessageBody knxTunnelingMessageBody)
             _sequenceCounter++;
         }
     }
-
-    void IObserver<KnxNetIpMessage>.OnCompleted() =>
-        _knxNetIpMessageSubject.OnCompleted();
-
-    void IObserver<IKnxMessage>.OnError(Exception error) =>
-        _knxMessageSubject.OnError(error);
-
-    void IObserver<IKnxMessage>.OnNext(IKnxMessage value) =>
-        _knxMessageSubject.OnNext(value);
-
-    void IObserver<IKnxMessage>.OnCompleted() =>
-        _knxMessageSubject.OnCompleted();
-
-    void IObserver<KnxNetIpMessage>.OnError(Exception error) =>
-        _knxNetIpMessageSubject.OnError(error);
-
-    void IObserver<KnxNetIpMessage>.OnNext(KnxNetIpMessage value) =>
-        _knxNetIpMessageSubject.OnNext(value);
 }