Ah, you are not using the correct method.
You are using
conn = new UDPConnection(conninfo, UDPOptions.None);
you should be using
conn = UDPConnection.GetConnection(conninfo, UDPOptions.None);
note, this is a static method so no ‘new’ statement. It’s implemented in this was so that if a connection already exists with the provided connectionInfo the existing connection can be returned instead.