Problem:
Connecting to InterBase for Linux with InterClient

Solution:
Try this database url:

jdbc:interbase://nt_server_name/linux_server_name:/absolute-path-to-file/file_name.gdb

where
  interserver is running on the nt server and
  interbase is running on the linux server

Also try connecting via the InterClient CommDiag utility using
host name of nt_server_name and
database file of linux_server_name:/absolute-path-to-file/file_name.gdb

Source: Paul Ostler