Update RtpClient.cs

Added using.

Signed-off-by: Julius R Friedman <juliusfriedman@users.noreply.github.com>

Rtp/RtpClient.cs

@@ -37,6 +37,7 @@ The above copyright notice and this permission notice shall be included in all c
 #endregion
 
 using Media.Common;
+using Media.Common.Extensions.Socket;
 using Media.Rtcp;
 using System;
 using System.Collections.Generic;