There are two PCs with Windows 10 x64 and Firebird 3.0.7 x64. The Firebird versions are identical. One of the PCs has a sample database. I can connect to it locally with no issues by using 'localhost/3050:<full_path_to_database>.
Whenever I try to connect to this database (IP_address/3050:<full_path_to_database>) from the other PC over the internet I get the 'connection rejected by remote interface' error. This error means that connection to the remote server had been established and (for whatever reason) closed by the remote service_mgr. I've tested the TCP connection via telnet and nmap - no problem, the port is open and the connection id successful.
Usually such thing happens when versions or types (32-64) differ between the server and the client. In my case, there are two identical(!) servers installed on both machines. And all traces of any former installations (fbclient.dll, gds32.dll, firebird.conf) have been removed.
Has anybody dealt with such thing? What else could be wrong?