Firewall issue

From: Rajat (myself_rajat_at_yahoo.com)
Date: 12/20/04 

Date: 19 Dec 2004 23:46:50 -0800

Dear All,

Can any body tell me. If there are two host and they are not able to
communicate directly to each other due to a firewall in between. Can
they able to communicate with each other by having a server as an
intermediate.

Though I know that until and unless we open a port for communication
at firewall they will not be able to intract each other. But someone
told me that we can overcome this thing by having a sever as an
intermediate. Is it possible?? If yes then HOW?? What special
functionalities that server will be having??

Waiting for some +ve responses.