Finally, there are three messages that may be used to find out about the network's topology. These are sendsys, version, and senduuname. They cause C News to return to the sender the sys file, a software version string, and the output of uuname(1), respectively. C News is very laconic about version messages; it returns a simple, unadorned ``C''.
Again, you should never issue such a message, unless you have made sure that it cannot leave a your (regional) network. Replies to sendsys messages can quickly bring down a UUCP network.