Refactor ConnectedClient statistics API

Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.Uwp.cs

@@ -43,6 +43,8 @@ namespace MQTTnet.Implementations
 
         public static Func<MqttClientTcpOptions, IEnumerable<ChainValidationResult>> CustomIgnorableServerCertificateErrorsResolver { get; set; }
 
+        public string Endpoint => _socket?.Information?.RemoteAddress?.ToString(); // TODO: Check if contains also the port.
+
         public async Task ConnectAsync(CancellationToken cancellationToken)
         {
             if (_socket == null)

Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs

@@ -41,6 +41,8 @@ namespace MQTTnet.Implementations
 
         public static Func<X509Certificate, X509Chain, SslPolicyErrors, MqttClientTcpOptions, bool> CustomCertificateValidationCallback { get; set; }
 
+        public string Endpoint => _socket?.RemoteEndPoint?.ToString();
+
         public async Task ConnectAsync(CancellationToken cancellationToken)
         {
             if (_socket == null)

Frameworks/MQTTnet.NetStandard/Implementations/MqttWebSocketChannel.cs

@@ -14,17 +14,20 @@ namespace MQTTnet.Implementations
         private readonly MqttClientWebSocketOptions _options;
 
         private WebSocket _webSocket;
-
+        
         public MqttWebSocketChannel(MqttClientWebSocketOptions options)
         {
             _options = options ?? throw new ArgumentNullException(nameof(options));
         }
 
-        public MqttWebSocketChannel(WebSocket webSocket)
+        public MqttWebSocketChannel(WebSocket webSocket, string endpoint)
         {
             _webSocket = webSocket ?? throw new ArgumentNullException(nameof(webSocket));
+            Endpoint = endpoint;
         }
 
+        public string Endpoint { get; }
+
         public async Task ConnectAsync(CancellationToken cancellationToken)
         {
             var uri = _options.Uri;