TCP/IP: the specified port number is not working, the default one does..

I have couple of  printers GK420t and GK420d. I change the ip-adress to permanent.

! U1 setvar "internal_wired.ip.protocol" "permanent"
! U1 setvar "internal_wired.ip.addr" "192.168.187.33"

! U1 setvar "internal_wired.ip.netmask" "255.255.255.0"

! U1 setvar "internal_wired.ip.port" "3000"

! U1 getvar "internal_wired.ip.protocol"
! U1 getvar "internal_wired.ip.addr"
! U1 getvar "internal_wired.ip.netmask"

! U1 getvar "internal_wired.ip.port"

I see that the feedback I got is right. (gives right IP and port)

When trying to communicatie over TCP/IP. I try to use 3000 but it is not working. Default one does work (9100)

"192.168.187.33" and 9100 = working

"192.168.187.33" and 3000 = not working

For my application I need to use 3000, I dont have alternative