Application Layer

Exploring the HTTP Protocol (Fail)

telnet www.dr-chuck.com 80

telnet www.dr-chuck.com 80
Trying 198.251.66.43...
Connected to www.dr-chuck.com.
Escape character is '^]'.
HELP


501 Method Not Implemented
...

Connection closed by foreign host.

Exploring the HTTP Protocol

telnet www.dr-chuck.com 80
Trying 198.251.66.43...
Connected to www.dr-chuck.com.
Escape character is '^]'.
GET http://www.dr-chuck.com/page1.htm HTTP/1.0

HTTP/1.1 200 OK
Last-Modified: Sun, 19 Jan 2014 14:25:43 GMT
Content-Length: 131
Content-Type: text/html

The First Page

If you like, you can switch to the Second Page.

Connection closed by foreign host.

The IMAP Protocol for Retrieving Mail

https://tools.ietf.org/html/rfc3501

C: A142 SELECT INBOX
S: * 172 EXISTS
S: * 1 RECENT
S: * OK [UNSEEN 12] Message 12 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * OK [UIDNEXT 4392] Predicted next UID
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: A142 OK [READ-WRITE] SELECT completed