[TriLUG] Port Numbers (was: email (imap) setup question)

[Mike Johnson]

Jim Ray [jim at neuse.net] wrote:
> Good stuff.  I can't remember which port is which.  They say the mind is
> the first to go.

There's also /etc/services for the more well known protocols.
 
> Question:
> How come the ports for SMTP, HTTP, etc indicate UDP and TCP?  I thought
> they used TCP.  I locked down this server so tight that nothing worked
> at all.  It was really cool.  Now, I'd like to selectively unlock it.  I
> tried TCP to no avail and think I might add UDP as well.

A lot of protocols have both TCP and UDP registrations, that doesn't
mean they use them.  Your normal SMTP and HTTP traffic is explicitly
TCP.  There's no need (or reason) to open 25/UDP and 80/UDP.
 
> On DHCP, is that the same thing as bootstrap protocol?

Sort of.  DHCP uses the BOOTP port (67/UDP for the server), but the
protocol on the wire is a bit different (you can cram more info in the
DHCP protocol).

Mike
-- 
"If life hands you lemons, YOU BLOW THOSE LEMONS TO BITS WITH 
 YOUR LASER CANNONS!" -- Brak

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