diff --git a/lib/csharp/src/Transport/TTLSServerSocket.cs b/lib/csharp/src/Transport/TTLSServerSocket.cs
index 9753d47..2e2d299 100644
--- a/lib/csharp/src/Transport/TTLSServerSocket.cs
+++ b/lib/csharp/src/Transport/TTLSServerSocket.cs
@@ -18,6 +18,7 @@
  */
 
 using System;
+using System.Net.Security;
 using System.Net.Sockets;
 using System.Security.Cryptography.X509Certificates;
 
@@ -53,6 +54,10 @@
         /// </summary>
         private X509Certificate serverCertificate;
 
+        /// <summary>
+        /// The function to validate the client certificate.
+        /// </summary>
+        private RemoteCertificateValidationCallback clientCertValidator;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="TTLSServerSocket" /> class.
@@ -82,7 +87,8 @@
         /// <param name="clientTimeout">Send/receive timeout.</param>
         /// <param name="useBufferedSockets">If set to <c>true</c> [use buffered sockets].</param>
         /// <param name="certificate">The certificate object.</param>
-        public TTLSServerSocket(int port, int clientTimeout, bool useBufferedSockets, X509Certificate2 certificate)
+        /// <param name="clientCertValidator">The certificate validator.</param>
+        public TTLSServerSocket(int port, int clientTimeout, bool useBufferedSockets, X509Certificate2 certificate, RemoteCertificateValidationCallback clientCertValidator = null)
         {
             if (!certificate.HasPrivateKey)
             {
@@ -92,6 +98,7 @@
             this.port = port;
             this.serverCertificate = certificate;
             this.useBufferedSockets = useBufferedSockets;
+            this.clientCertValidator = clientCertValidator;
             try
             {
                 // Create server socket
@@ -143,7 +150,7 @@
                 client.SendTimeout = client.ReceiveTimeout = this.clientTimeout;
 
                 //wrap the client in an SSL Socket passing in the SSL cert
-                TTLSSocket socket = new TTLSSocket(client, this.serverCertificate, true);
+                TTLSSocket socket = new TTLSSocket(client, this.serverCertificate, true, this.clientCertValidator);
 
                 socket.setupTLS();
 
diff --git a/lib/csharp/src/Transport/TTLSSocket.cs b/lib/csharp/src/Transport/TTLSSocket.cs
index 9e1f9f2..ca8ee41 100644
--- a/lib/csharp/src/Transport/TTLSSocket.cs
+++ b/lib/csharp/src/Transport/TTLSSocket.cs
@@ -77,10 +77,12 @@
         /// <param name="client">An already created TCP-client</param>
         /// <param name="certificate">The certificate.</param>
         /// <param name="isServer">if set to <c>true</c> [is server].</param>
-        public TTLSSocket(TcpClient client, X509Certificate certificate, bool isServer = false)
+        /// <param name="certValidator">User defined cert validator.</param>
+        public TTLSSocket(TcpClient client, X509Certificate certificate, bool isServer = false, RemoteCertificateValidationCallback certValidator = null)
         {
             this.client = client;
             this.certificate = certificate;
+            this.certValidator = certValidator;
             this.isServer = isServer;
 
             if (IsOpen)
@@ -251,27 +253,16 @@
         /// </summary>
         public void setupTLS()
         {
+            this.secureStream = new SslStream(this.client.GetStream(), false, this.certValidator ?? CertificateValidator);
             if (isServer)
             {
                 // Server authentication
-                this.secureStream = new SslStream(this.client.GetStream(), false);
-                this.secureStream.AuthenticateAsServer(this.certificate, false, SslProtocols.Tls, true);
+                this.secureStream.AuthenticateAsServer(this.certificate, this.certValidator != null, SslProtocols.Tls, true);
             }
             else
             {
                 // Client authentication
-                X509CertificateCollection validCerts = new X509CertificateCollection();
-                validCerts.Add(certificate);
-
-                if (this.certValidator != null)
-                {
-                    this.secureStream = new SslStream(this.client.GetStream(), false, new RemoteCertificateValidationCallback(this.certValidator));
-                }
-                else
-                {
-                    this.secureStream = new SslStream(this.client.GetStream(), false, new RemoteCertificateValidationCallback(CertificateValidator));
-                }
-                this.secureStream.AuthenticateAsClient(host, validCerts, SslProtocols.Tls, true);
+                this.secureStream.AuthenticateAsClient(host, new X509CertificateCollection { certificate }, SslProtocols.Tls, true);
             }
 
             inputStream = this.secureStream;