Internet -- Under the Covers

This document is intended to be used to educate people on how internet software works by introducing the underlying protocols, how internet software makes use of those, and how to troubleshoot problems using the underlying protocols. After reading this document and following the examples, you will be able to, using just a telnet program:
In addition, you will be able to:

This section is split into several parts:
The Web: The HTTP Protocol
Receiving Mail: The POP3 Protocol
Sending Mail: The SMTP Protocol
Usenet News: The NNTP Protocol
Network Abuse - Omitted

I have omitted the section on Network Abuse here because it contains "open secrets" about the Internet that describe vulnerabilities. Publishing these details would not make me the first, but I am still reluctant to do so. If you need information about how abuse happens, or more detail on any of the protocols, please mail me.
This document written and coded in HTML by Pat Gunn