You can create as many TCP inputs as you like (within reason, I'm sure), and run a simulator instance to push to each one. Regarding which ports to use, you can specify those. I typically stay around the neighborhood of the default, i.e. 5566, 5567, 5570, etc. A TCP input's port is specified in the Advanced properties, as seen below, where I created a new TCP input with port 5566 (click image to enlarge):
and then specify that port in your Simulator, as seen below:
Windows command to list ports currently in use: netstat -o -a
Run the latter command from within a Windows command console window to see which ports are in use by which PID (program identifiers) on your system. Like Mark said, on my local system, I usually find no conflicts when using ports in the 5500 - 5600 range for TCP/Text input.