How to do it…

You can get this information from the pg_stat_activity view, as it includes the connected clients' IP address, port, and hostname (where applicable). The port is only needed if you have more than one connection from the same client computer and you need to do further digging to see which process there connects to which database. Run the following command:

SELECT datname, usename, client_addr, client_port,
       application_name FROM pg_stat_activity;

The client_addr and client_port parameters help you look up the exact computer and even the process on that computer that has connected to the specific database. You can also retrieve the hostname of the remote computer through the client_hostname option (this requires log_hostname to be set to on).