May I ask why are you trying to create or think you need a second connection?
The way NetworkComms.Net is currently configured it is not possible to have more than one connection between 2 applications with identical IP addresses at both endpoints. What is possible is multiple connections over independent IP addresses/adaptors. This was done to help enforce connection integrity in the absence of any necessary use case. Once a connection has been created it is completely thread safe regardless of where/how it is used subsequently.
This is why in the first example you gave the initial connection is automatically closed due to the creation of the second and also why the second example works.