Parallels will set up networking in one of three ways you chose. With "bridged networking" it connects the VM to the networking adapter you choose (current default or force to Ethernet, Wifi, or anything else you have). In this case in a typical environment your router (or server) will assign an IP address just like it does with your Mac, as it looks like a separate system. You can also go with "shared networking" in which case it shares the IP address with your Mac. I would suspect (haven't verified) that it uses port forwarding and basically sets up its own local network between the VM and the Mac. Finally there is "Host Only networking" where the VM can only access the Mac. This is good if you want it to run if a walled environment.
Yes you can access the VM via TCP. I've demoed a networked application running two Windows VMs simultaneously with the networked application running on the Mac and both VMs, all communicating with each other.