If the other addresses are always different, then don't worry about it. If it was all coming from one address then it may be someone trying to pull something on you, but if the hits are all from different IP addresses, it's just static. On cable or DSL, you'll get alerts every minute or two if you leave your firewall set up to show them all. It's normal.
Other computers running various programs will occasionally try to find other additional computers running the same program. It can be a virus, but often it is just file-sharing programs, searching for other computers with files to share.
There are lists online of programs and the ports they commonly default to, but the problem with these lists now is that many file-sharing programs have port
ranges enabled, and (in an effort to make them more difficult to filter out) they will use a random assortment of ports in these ranges. A couple different pages I found said 1554 is the default port for the "CACI license manager", but that doesn't guarantee this is what is hitting on your PC:
www.keir.net/portlist.html ~