NNTP is the client server protocol which defines the format and syntax and content of a conversation between two computers. These two are not just talking about the weather, you know: they are exchanging newsgroup articles! The protocol is defined by RFC977.
Your TSX system uses NNTP in several different places. If you get your newsgroup feed straight from your provider, which initiates connections to your system to send in news articles, then these connections fire up the NNTPTOSS program. NNTPTOSS and the provider speak NNTP-ese about the articles coming into your system. Similarly, if you post outgoing articles to your provider, the USESCAN program will connect to the provider and conduct the same sort of conversation in the reverse direction.
You don't need to know NNTP yourself, since your TSX programs speak it well. However, if you are curious about it, and have the USESCAN program running, have a look in the USENET event log; it displays the conversation taking place. You have to activate that logging in SYSOP, under general setup, debug control. If you want to know more about NNTP, see the RFC.
NNTP has been enhanced some since the original RFC was promulgated. In December 1996, for example, we added support in the NNTPTOSS program for extended commands used to specify a username and password. For the latest up to date info you better call us.