Check if Postgresql is listening

Question

Given an IP Address and port number, is it possible to check if the machine with that IP address has Postgresql listening on the specified port? If so, how?

I just want

Answer 1

In brief

In details

Fastest way is to use netcat aka nc with timeout ability as shared here

Results as 0/1 means postgres working/not-working

echo 'QUIT' | nc -w SECONDS YOUR_HOST PORT; echo $?
# eg
echo 'QUIT' | nc -w 1       localhost 5432; echo $?

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Another also-faster way that works for me is to use telnet as discussed here.

echo -e '\x1dclose\x0d' | telnet YOUR_HOST PORT
# eg
echo -e '\x1dclose\x0d' | telnet localhost 5432