Will have a better look at it later today - but as a quick one is the mscomm control required for the server as I can't see any code that refers to a serial port in there.
Quick update:
In your server try using
' Return the data received from the client to the console.
Dim ClientData As String
ClientData = Encoding.ASCII.GetString(Encoding.ASCII.Convert(Encoding.Unicode, Encoding.ASCII, bytes))
in place of your existing
' Return the data received from the client to the console.
Dim ClientData As String = Encoding.ASCII.GetString(bytes)