serverName

Hostname or IP address of the server, or several separated by commas - db1,db2:5433,[::1]:5434 - each with a port of its own or portNumber's. Defaults to localhost.

Several are tried in turn until one becomes a connection; targetSessionAttrs says which kind of server that may be, and loadBalanceHosts in what order they are tried. An IPv6 address with a port of its own goes in brackets; a lone one without may go bare.