SHELL

could not connect to server: Connection refused Is the server running on host and accepting TCP/IP connections on port 5432?

cd /etc/postgresql/9.x/main/
------- open file named postgresql.conf
sudo nano postgresql.conf
------- add this line to that file
listen_addresses = '*'
------- then open file named pg_hba.conf
sudo nano pg_hba.conf
------- and add this line to that file
host  all  all 0.0.0.0/0 md5
------- restart your server
sudo /etc/init.d/postgresql restart

could not connect to server: Connection refused Is the server running on host "localhost" (::1) and accepting TCP/IP connections on port 5432

// In my case PostgreSQL updates from version 13.4 to 14 in background, so it fixes by:
	brew postgresql-upgrade-database
// In other case the problem fixed by:
	rm -rf /usr/local/var/postgres/postmaster.pid
// Restart service postgresql:
	brew services restart postgresql
// How can you understand what is the problem?
// For first see what service is not correct started:
	brew services list
// For second show file postgres.log, where will be the error:
	tail -f /usr/local/var/log/postgres.log
// And so find answer by this error's text

connection to server at "localhost" (::1), port 5432 failed: Connection refused Is the server running on that host and accepting TCP/IP connections

FATAL:  lock file "postmaster.pid" already exists
 HINT:   Is another postmaster (PID 379) running in data directory "/usr/local/var/postgres"?