How to enable or disable connection protocols for Firebird on Windows

Firebird on Windows has the following switches to explicitly enable connection protocols:
-i enables INET protocol, it is used when the connection string looks like localhost:Disk\Path\database.fdb or server_name:
 

C:\HQbird\Firebird30>firebird  -a

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  localhost:o:\OLTP30.V20190415.FDB
Database: localhost:o:\OLTP30.V20190415.FDB, User: SYSDBA
SQL> exit;

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  xnet://o:\OLTP30.V20190415.FDB
Database: xnet://o:\OLTP30.V20190415.FDB, User: SYSDBA
SQL> exit;

C:\HQbird\Firebird30>firebird  -a  -x

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  localhost:o:\OLTP30.V20190415.FDB
Statement failed, SQLSTATE = 08006
Unable to complete network request to host "localhost".
-Failed to establish a connection.
Use CONNECT or CREATE DATABASE to specify a database
SQL> exit;

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  xnet://o:\OLTP30.V20190415.FDB
Database: xnet://o:\OLTP30.V20190415.FDB, User: SYSDBA
SQL> exit;

C:\HQbird\Firebird30>firebird  -a  -i

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  localhost:o:\OLTP30.V20190415.FDB
Database: localhost:o:\OLTP30.V20190415.FDB, User: SYSDBA
SQL> exit;

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  xnet://o:\OLTP30.V20190415.FDB
Statement failed, SQLSTATE = 08006
Unable to complete network request to host "xnet://Global\FIREBIRDHQBIRD".
Use CONNECT or CREATE DATABASE to specify a database
SQL> exit;

C:\HQbird\Firebird30>firebird  -a  -i -x

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  localhost:o:\OLTP30.V20190415.FDB
Database: localhost:o:\OLTP30.V20190415.FDB, User: SYSDBA
SQL> exit;

C:\HQbird\Firebird30>isql -user SYSDBA -pass masterkey  xnet://o:\OLTP30.V20190415.FDB
Database: xnet://o:\OLTP30.V20190415.FDB, User: SYSDBA
SQL> exit;