Port 6379: Redis

What is Port 6379?

Port 6379 is the default port for Redis, an open-source in-memory data structure store. Redis is commonly used for caching, session storage, message queuing, and real-time analytics.

Connection Examples

# redis-cli
redis-cli -h localhost -p 6379
redis-cli -h localhost -p 6379 -a password

# Connection URL
redis://localhost:6379
redis://:password@localhost:6379/0
rediss://localhost:6379  # TLS

# Node.js (ioredis)
const Redis = require('ioredis');
const redis = new Redis({
  host: 'localhost',
  port: 6379,
  password: 'secret'
});

# Python
import redis
r = redis.Redis(host='localhost', port=6379, password='secret')

Security Configuration

# /etc/redis/redis.conf

# Bind to localhost only (safe default)
bind 127.0.0.1 ::1

# Set a strong password
requirepass your_strong_password_here

# Disable dangerous commands
rename-command FLUSHDB ""
rename-command FLUSHALL ""
rename-command DEBUG ""
rename-command CONFIG ""

# Restart Redis
sudo systemctl restart redis

Common Use Cases

• Caching: Store frequently accessed data in memory
• Session storage: Store user sessions for web apps
• Rate limiting: Track request counts with TTL
• Message queue: Pub/Sub for real-time messaging
• Leaderboards: Sorted sets for rankings

Basic Commands

# Test connection
redis-cli ping
# Response: PONG

# Set and get values
SET mykey "Hello"
GET mykey

# Set with expiration (seconds)
SETEX session:123 3600 "user_data"

# Check TTL
TTL session:123

# List all keys (use carefully in production)
KEYS *

# Get server info
INFO

Troubleshooting

# Check if Redis is running
sudo systemctl status redis
sudo ss -tlnp | grep 6379

# Test connection
redis-cli ping
redis-cli -a password ping

# Check what Redis is bound to
redis-cli CONFIG GET bind

# Monitor commands in real-time
redis-cli monitor

# Check memory usage
redis-cli INFO memory

Common Issues

• NOAUTH: Authentication required - provide password
• Connection refused: Redis not running or wrong bind address
• OOM: Out of memory - increase maxmemory or eviction policy
• Slow operations: Check for blocking commands with SLOWLOG