Juraj:
I do not understand. How does my recommendation imply unlimited connections?
If there are a limited number of connections (like the Ethernet shield can only handle 4 simultaneous connections), and you use one of them for a telnet session, so that you can be told twice a day that the door opened or closed, then that connection is not available for any other use. Hence it is tied up.
nothing is tied up.
It that one connection is nothing, this implies, to me, at least, that it isn't 1 of 4. Rather, it is one of so many that one doesn't matter.
So, which is it? Are you tying up one of a limited number of connections, where it could matter, or one of so many that it doesn't matter?