From the firebird embedded readme:
2.2. Database access
Client access can be only via the local protocol,
i.e. NOT a TCP/IP connection string that includes
the server name "localhost" or IP address 127.0.0.1.
The embedded server supports only the local connect
to a database file path without a server name. The
client program gets an exclusive access to the
database file after successful connect.
The embedded server acts as a true local server for a single
client accessing databases on a local machine. It can also
act as a remote gateway that redirects all network calls to
other hosts, just as the regular client library
does.
Kind Regards,
Keith Blows