P5 is checking the network to see if any other copies of itself are in use. If it finds another P5, it compares serial number and similar information, and if they match, it will not start. After that, it stops looking.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)