Typically, the default port (1700 or 1717) set in your license file will be fine. However, you may find that there is another license manager running on one of those ports. If you select a port that is in use, you will see something like the following in you license server debug log file:

18:23:28 (lmgrd) The TCP port number in the license, 1717, is already in use.

Edit your license file and try another port such as 1700 or 1718.