<<thank you for help.
i have did:
launchctl unload org.firebird.gds.plist
launchctl load org.firebird.gds.plist
bevor your mail and again after your mail.
but this cant fix the problem then my failure was based on a mistake of the real function of the /etc/services file.

the original line in /etc/services looks like :
gds_db 3050/udp # gds_db
gds_db 3050/tcp # gds_db

and many lines lower i have set my own entries:
gds_db 5143/udp # gds_db (buhl)
gds_db 5143/tcp # gds_db (buhl)

but without disabling (comment) the upper entries.

so in my /etc/services was the gds_db enries „doubled“ set.
wow, this was the failure!>>

Err yes. Just a bit.

<<now it works as expected.>>

As it does for me.

<<i have meant bevore, all entries in this file can simple set or changed as needed.
but because the upper entries was processed earlier,
(maybe) the lower entries was ignored then.
is this a special design from firebird?>>

Nope. gds_db = interbase/firebird = 3050 as per IANA
http://linux.about.com/library/cmd/blcmdl5_services.htm

Regards
Paul