Chapter 9 CHAPTER 9 NNTP Clients and Servers Usenet is a long-standing network of servers used for public discussion on the Inter- net. Each discussion forum in Usenet is called a newsgroup, and each Usenet server can host any number of newsgroups. Messages in a Usenet newsgroup are referred to as articles. Usenet servers communicate with each other to keep their copies of each newsgroup up-to-date, so that an article posted to a newsgroup on one server will eventually propagate to all the servers that host that newsgroup. This setup allows many people to participate in Usenet discussions without putting the load on any one central server. The Usenet system dates back to before the Internet and TCP/IP had become widely