issue with reading hostname

psql postgres -A -t -p 5432 -h /tmp/ -c 'SELECT pg_is_in_recovery();'

so below are my questions:

1. Is the psql client reading the socket file that resides in the /tmp directory to fetch the hostname ?

2. I saw the socket file in /tmp and it is empty. Then how is the psql client still reading the socket file successfully for hostname ?

this is my socket looks ( the size is 0 as the file is empty):

srwxrwxrwx.  1 postgres postgres      0 Apr 22 12:47 .s.PGSQL.5432

Please help me clarify these doubts.

Regards.