PostgreSQL Connection Fix for Linux Server

We are looking for an experienced Linux server administrator or DevOps professional to troubleshoot and fix a PostgreSQL connection issue on our Apache/Passenger-based application.

Issue Details:
-Our application fails to connect to the PostgreSQL database and shows the following error:

"connection to server at "172.17.0.1", port 5433 failed: Connection refused
Is the server running on that host and accepting TCP/IP connections?"

-The issue seems to be related to database connectivity, firewall settings, or server configuration.
-The PostgreSQL database is running on port 5433, not the default 5432.
-The application is deployed using Apache + Passenger.

Expected Fix:
-Diagnose and fix the PostgreSQL connection issue.
-Ensure the application can successfully connect to the database.
-Verify and update PostgreSQL, firewall, and network configurations if needed.
-Restart necessary services (Apache, Passenger, PostgreSQL) after the fix.
-Provide documentation on what was changed for future reference.

Requirements:
-Experience with Linux servers (Ubuntu or Debian preferred).
-Strong knowledge of PostgreSQL configuration and troubleshooting.
-Experience with Apache + Passenger.
-Familiarity with Docker (if the database is running inside a container).

If you are confident in fixing this issue, please apply with:
-Your relevant experience
-Estimated time to complete the fix
-Any clarifying questions

Looking forward to working with an expert who can resolve this quickly!