Port 5432: PostgreSQL Database

What is Port 5432?

Port 5432 is the default port for PostgreSQL, a powerful open-source relational database. It's widely used in modern web applications and supports advanced features like JSONB, full-text search, and extensions.

Connection Examples

# psql command line
psql -h hostname -p 5432 -U username -d database

# Connection string (URI format)
postgresql://user:password@localhost:5432/database
postgres://user:password@localhost:5432/database?sslmode=require

# Node.js (pg)
const pool = new Pool({
  host: 'localhost',
  port: 5432,
  user: 'postgres',
  password: 'secret',
  database: 'myapp'
});

# Python (psycopg2)
conn = psycopg2.connect(
    host="localhost",
    port=5432,
    user="postgres",
    password="secret",
    database="myapp"
)

Configuration Files

# Find config file location
sudo -u postgres psql -c "SHOW config_file;"
# Typically: /etc/postgresql/14/main/postgresql.conf

# postgresql.conf - listen on all interfaces (be careful!)
listen_addresses = 'localhost'  # Safe default
# listen_addresses = '*'  # All interfaces (needs pg_hba.conf)

# Change port
port = 5432

# Restart PostgreSQL
sudo systemctl restart postgresql

Client Authentication (pg_hba.conf)

# /etc/postgresql/14/main/pg_hba.conf

# TYPE  DATABASE  USER  ADDRESS       METHOD

# Local connections
local   all       all                 peer
host    all       all   127.0.0.1/32  scram-sha-256
host    all       all   ::1/128       scram-sha-256

# Allow specific IP (internal network only)
host    all       all   10.0.0.0/8    scram-sha-256

# Reload after changes
sudo systemctl reload postgresql

SSL Connections

# Check if SSL is enabled
psql -c "SHOW ssl;"

# Connection string with SSL
postgres://user:pass@host:5432/db?sslmode=require
postgres://user:pass@host:5432/db?sslmode=verify-full

# SSL modes:
# disable  - No SSL
# allow    - Try non-SSL first
# prefer   - Try SSL first (default)
# require  - Must use SSL
# verify-ca - Verify server cert
# verify-full - Verify cert + hostname

Troubleshooting

# Check if PostgreSQL is running
sudo systemctl status postgresql
sudo ss -tlnp | grep 5432

# Check what address it's listening on
sudo -u postgres psql -c "SHOW listen_addresses;"

# Test connection
nc -zv localhost 5432
psql -h localhost -U postgres

# View connection errors
sudo tail -f /var/log/postgresql/postgresql-14-main.log

Common Issues

• FATAL: no pg_hba.conf entry: Add client IP to pg_hba.conf
• Connection refused: Check listen_addresses and service status
• Password authentication failed: Verify credentials and auth method
• Too many connections: Increase max_connections or use connection pooler

How to Check if Port 5432 is Open

These commands help verify PostgreSQL connectivity from client and server side.

# From a remote machine
nc -zv db-server.example.com 5432
nmap -p 5432 db-server.example.com
psql -h db-server.example.com -p 5432 -U postgres

# On the server — check if PostgreSQL is listening
sudo ss -tlnp | grep 5432
sudo lsof -i :5432

# Check PostgreSQL listen address
sudo -u postgres psql -c "SHOW listen_addresses;"

# Check pg_hba.conf for client auth rules
sudo -u postgres psql -c "SHOW hba_file;"

# Check firewall
sudo ufw status | grep 5432

Connection Pooling with PgBouncer

PostgreSQL creates a new process per connection, which can exhaust resources under load. PgBouncer sits between your app and PostgreSQL to reuse connections efficiently.

# PgBouncer typically listens on port 6432
# /etc/pgbouncer/pgbouncer.ini
[databases]
myapp = host=127.0.0.1 port=5432 dbname=myapp

[pgbouncer]
listen_port = 6432
listen_addr = 127.0.0.1
pool_mode = transaction
max_client_conn = 1000
default_pool_size = 25

# App connects to PgBouncer instead of PostgreSQL directly
postgresql://user:pass@localhost:6432/myapp

Monitoring PostgreSQL with UptimeSignal

PostgreSQL downtime on port 5432 causes 500 errors in your application. UptimeSignal monitors your application's health endpoints, alerting you when database issues start affecting users. Combine with port monitoring for MySQL and Redis for full infrastructure coverage.

Frequently Asked Questions