TCP Port Monitoring

Monitor the availability of TCP ports on your servers. Perfect for databases, mail servers, game servers, and any custom TCP-based services.

What is TCP Monitoring?

TCP monitoring checks if a specific port on your server is open and accepting connections. It attempts to establish a TCP connection to the specified host and port, verifying that your service is accessible.

Unlike HTTP monitoring, TCP monitoring works at a lower network level and can monitor any TCP-based service, not just web services.

Configuration

Host and Port

Specify the hostname or IP address and the TCP port number to monitor.

Format: tcp://hostname:port

Examples:
• tcp://database.example.com:3306
• tcp://mail.example.com:25
• tcp://192.168.1.100:8080
• tcp://game-server.example.com:25565

Connection Timeout

Maximum time to wait for a successful TCP connection. Default is 10 seconds. Adjust based on network latency and service response times.

Check Frequency

How often to check the TCP port. Options range from 10 seconds to 60 minutes. Consider the criticality of the service when setting frequency.

Common TCP Ports

Here are commonly monitored TCP ports and their typical services:

Database Servers

  • 3306 - MySQL/MariaDB
  • 5432 - PostgreSQL
  • 27017 - MongoDB
  • 6379 - Redis
  • 1433 - Microsoft SQL Server
  • 9042 - Cassandra

Mail Servers

  • 25 - SMTP
  • 587 - SMTP (submission)
  • 110 - POP3
  • 995 - POP3S (secure)
  • 143 - IMAP
  • 993 - IMAPS (secure)

Web & Application Servers

  • 80 - HTTP
  • 443 - HTTPS
  • 8080 - HTTP alternate
  • 3000 - Node.js apps
  • 8000 - Django/Python apps
  • 9000 - PHP-FPM

Other Services

  • 22 - SSH
  • 21 - FTP
  • 3389 - RDP (Windows)
  • 5900 - VNC
  • 25565 - Minecraft
  • 27015 - Source games

Use Cases

Database Monitoring

Ensure your database servers are accepting connections:

  • • Monitor primary and replica database servers
  • • Check database cluster endpoints
  • • Detect when database ports become unreachable
  • • Get notified if firewall rules change unexpectedly

Mail Server Monitoring

Keep email services running smoothly:

  • • Monitor SMTP port availability (25, 587, 465)
  • • Check IMAP/POP3 port accessibility
  • • Detect if mail server ports are blocked
  • • Ensure secure ports remain open for clients

Custom Application Monitoring

Monitor any TCP-based service:

  • • Game servers for player connectivity
  • • Message queues and brokers
  • • Custom protocols and services
  • • Internal microservices

Best Practices

  • ✓
    Monitor from multiple regions

    Ensure global accessibility and detect regional network issues

  • ✓
    Set appropriate timeouts

    Consider network latency and normal connection times for your service

  • ✓
    Monitor all critical ports

    Don't just monitor HTTP - check databases, caches, and supporting services

  • ✓
    Use with HTTP monitoring

    Combine TCP and HTTP checks for complete application monitoring

Limitations

What TCP Monitoring Doesn't Check

  • •
    Application logic: Only verifies port is open, not that the application is functioning correctly
  • •
    Authentication: Cannot verify login credentials or authentication mechanisms
  • •
    Data integrity: Doesn't validate data or query responses
  • •
    SSL/TLS: For encrypted connections, use HTTP/HTTPS monitoring instead

For application-level monitoring, consider using HTTP/HTTPS monitors with health check endpoints.

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