Unix Domain Socket Location

All Postgres servers support TCP/IP connections, including localhost connections that allow clients to connect to servers on
the same machine. Unix-like operating systems also support local
or Unix-domain socket connections. These connections do not use the TCP/IP stack but rather a more efficient stack for local
connections. (I previously showed that Unix-domain socket communication
is measurably faster.)

Unix-domain socket connections require a socket file in the local file system. These are not normal files but more like entry points to
listening servers. By default, Postgres places these socket files in the /tmp directory:

srwxrwxrwx  1 postgres postgres    0 Jul 30 20:27 .s.PGSQL.5432=

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