Install remserial:

http://lpccomp.bc.ca/remserial/

Start with:

remserial -d -r server-name -p 23000 -l /dev/remserial1 /dev/ptmx &

Start grig with:

grig -m 228 -r /dev/remserial1

http://www.linuxquestions.org/questions/ubuntu-63/ubuntu-8.04-or-8.10-help-with-serial-ports...-688346/

Problem solved:

check number of supported and activated serial ports in kernel config:

# grep UARTS /boot/config-2.6.x-y-server CONFIG_SERIAL_8250_NR_UARTS=48 CONFIG_SERIAL_8250_RUNTIME_UARTS=4

To increase the number of serial ports activated, change grub configuration. The line starting with kernel … should be modified to include the number of serial ports to activate:

kernel /vmlinuz-2.6.x-y-server … 8250.nr_uarts=8

Reboot, and check number of serial ports: