Um, I think he meant what doesn't multiplex their connections (like how a web browser always hits destination 80, but has a random source > 1024).

Anyway, the only protocol I can think of that always uses the same source port is NTP. That always comes from 123 going to port 123. I can't think of anything else off-hand that acts like that, though.

Hello Adam,

yes but this happens also because NTP uses UDP port 123 and UDP misses the socket concept or at least it is not the same as TCP does.

Once I thought that UDP could have a socket concept like TCP, but examples like NTP and also SNMP and SNMP traps show it is different.

Hope to help

Giuseppe

so are there any programs that use this? I thought FTP used it ?

Well, active FTP connections can, I believe.

http://slacksite.com/other/ftp.html

And as said, NTP always comes from 123 to 123.