OSE & Firewall

There is a firewall between Application Server iAS9i and Oracle(8.1.7) with two opened ports 1521 and 2020,
any client from iAS9i sql*plus, jdbc, mod_plsq are working fine, but mod_ose gives me a problem.

on Apache log file I get:
Cannot connect statefully to AuroraServer for INST1_HTTP

on Database listener.log everything is OK:
(CONNECT_DATA=(SERVICE_NAME=MODOSE)(SERVER=SHARED)
(PRESENTATION=http://testService)) * (ADDRESS=(PROTOCOL=tcp)
(HOST=blah03)(PORT=48123)) * establish * MODOSE * 0

It sounds like I have only stateless connection and couldn't establish statefull.
When I do test without a firewall: everythings is working fine, but with
firewall...it gives me 503 erorr.
Who knows where the problem is?

my settings:
I have two endpoints on testService:
 -port 2020 main
 -net8 testServiceNet8

in init.ora:
mts_dispatchers=(PROTOCOL=tcp)(SER=MODOSE)

-- 
Thanks,
Andrei Zoubakine