How to fix ERR Got an unexpected reply from Redis (node-redis pubsub) in Redis

# Check Redis server version
redis-cli INFO server | grep redis_version

# Check node-redis version in your project
npm list redis

# Test basic connectivity
ping redis-server-host

# Test Redis connectivity with telnet
telnet redis-server-host 6379
# Type 'PING' and press Enter - should return '+PONG'

# Check for packet loss
mtr redis-server-host

# Check current MTU
ip link show | grep mtu

# If using Docker or Kubernetes, check container network settings
docker inspect container_name | grep -i mtu

# Check memory usage
redis-cli INFO memory | grep -E '(used_memory|maxmemory|mem_fragmentation_ratio)'

# Check connected clients and pubsub stats
redis-cli INFO clients
redis-cli INFO stats | grep -E '(total_connections_received|rejected_connections|pubsub_channels)'

# Check for slow logs
redis-cli SLOWLOG GET 10

# Monitor Redis in real-time
redis-cli MONITOR | head -50

# Update node-redis
npm install redis@latest

const client = createClient({
  url: 'redis://localhost:6379',
  socket: {
    reconnectStrategy: (retries) => {
      if (retries > 10) {
        console.error('Too many reconnection attempts');
        return new Error('Too many retries');
      }
      return Math.min(retries * 100, 3000);
    }
  }
});

client.on('error', (err) => {
  console.error('Redis client error:', err);
  // Implement your error recovery logic here
});

client.on('end', () => {
  console.log('Redis client disconnected');
});

// test-pubsub.js
import { createClient } from 'redis';

async function testPubsub() {
  const publisher = createClient({ url: 'redis://localhost:6379' });
  const subscriber = createClient({ url: 'redis://localhost:6379' });

  await publisher.connect();
  await subscriber.connect();

  // Simple string message
  await subscriber.subscribe('test-channel', (message) => {
    console.log('Received:', message);
  });

  await publisher.publish('test-channel', 'simple test message');
  await new Promise(resolve => setTimeout(resolve, 1000));

  // JSON message
  await publisher.publish('test-channel', JSON.stringify({ test: 'data' }));
  await new Promise(resolve => setTimeout(resolve, 1000));

  await publisher.quit();
  await subscriber.quit();
}

testPubsub().catch(console.error);

const client = createClient({
  url: 'redis://localhost:6379',
  socket: {
    tls: false,
  }
});

// Enable debug mode
import { commandOptions } from 'redis';

// Or set environment variable
// DEBUG=redis:* node your-app.js

# Capture Redis traffic (adjust interface as needed)
sudo tcpdump -i any port 6379 -w redis-traffic.pcap

# Or use tshark for immediate analysis
sudo tshark -i any -f 'port 6379' -V | grep -A5 -B5 'PUBLISH\|SUBSCRIBE'