I have a linux(debian server) based gateway on my LAN, now i need priorize the externals connections by port (to debian server), is possible priorize it with QoS (e.g. all traffic to port 5800 set prio 1, all rest of traffic set prio 99) ?, and i need recompile the kernel for do it?

I look for a simple solution, but the examples I saw are for more complete system.

thanks you and sry for my bad english

Have a look at the LARTC Example of a full nat solution with QoS*?

first: Read the documentation!! http://lartc.org/howto
yes, i know, it is toomuch... but it pays off

for make you a little short, i use HTB on the internet access, but to prioritize outbound traffic.
see http://lartc.org/howto/lartc.cookbook.ultimate-tc.html

in my case, the bottleneck is in the upload part of the link, so the right thing to do if i had in your situation is to give max priority to the connections coming from tcp/22 and tcp/5900 on my lan/dmz.

if you read the entire howto, you will get a really more comprehensive point of view of your problem and you will be able to design the better solution to it

best regards