Editing Virtual1's Hotline Server Protocol Guide (section)

===Chapter 4: LOGGING IN===

Before sending a login, you must establish a "pipe". Do this by
connecting to the port and then exchanging this "handshake" with
the server:
 CLIENT HELLO
   • "TRTPHOTL"  identifies this is a hotline client
   • short (1) minimum server version this client is compatible with?
   • short (2) client version?
 
 TRTPHOTL (0) (1) (0) (2)
 
 SERVER HELLO
   •"TRTP"
   • long (errorcode) - 0=OK you are connected, 1=rejected
 
 TRTP (0) (0) (0) (0)

Once these have been exchanged, you can assume you are connected
to a HL server and can proceed to login. Until you have received
a success reply to your login transaction, the only other
transaction you can submit is a request for disconnect.
(I think all others are just ignored?)

Once logged in, you are by no means required to request a userlist,
request news, or do anything else for that matter. Hinks' client
will send the login and then immediately fire off a request for the
agreement, userlist and news, before even receiving confirmation of
a successful login. (how rude!)