@valdir.marcos, the program worked on the server, so I guess everything is set correctly.
If I run my program on the server everything works fine.
Ferenc, did you use the same host-settings (i.e. IP of the local network) in the program when testing on the server?
With the client installation of Firebird 3.0, do you still get the option on the last page to create a legacy gds32.dll in the Windows-directories?
Try a client install with checking that option.
I see the TIBConnection first searches for fbclient.dll and then for gds32.dll. But the fbclient.dll is not in the search path and needs to be extracted from registry settings. If that's not done the fbclient.dll can't be found. You could try to copy the fbclient.dll in your program directory but it could be that it needs extra files.
(also note that for a 64bit installation the 32bit fbclient.dll is in WOW64)
*) So first try the 32bit client install again on the workstation to see if you can install the legacy dll.
*) Second, copy the fbclient.dll (make sure you have the correct bitness) to your program directory.
*) Third, remove it again and make sure your firebird-bin directory is in the system search path (possible restart required).