Finding the port that a PostgreSQL instance is using can be challenging due to various installation methods and default ports. To determine the port, one must consider different platforms such as Linux, Windows, and macOS, each with unique installation directories and configuration files. On Linux systems, running `ps -ef | grep -i postgres` followed by `sudo netstat -plnt | grep postgres` can help identify the process ID of the PostgreSQL instance, which is then used to retrieve the port number from commands such as `netstat -anv | grep <PID>` or checking the `installation_summary.log` file. On Windows, navigating to the installation directory and searching for logs or using PowerShell with the command `Get-NetTCPConnection | Select-Object LocalPort, OwningProcess | ForEach-Object { $_ | Add-Member -MemberType NoteProperty -Name ProcessName -Value (Get-Process -Id $_.OwningProcess).Name -PassThru }` can help identify the port number. On macOS, checking the `installation_summary.log` file or using the process ID with the command `netstat -anv | grep <PID>` can also determine the port number. Additionally, some cloud services like Timescale Cloud provide a connection string that includes the port number when launching an instance.