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MonitoringTCP/UDP Checks

TCP/UDP Checks

TCP/UDP checks monitor network services at the socket level, useful for non-HTTP services.

When to Use TCP/UDP Checks

Use TCP/UDP checks for services that don’t use HTTP:

  • Database servers - MySQL (3306), PostgreSQL (5432), Redis (6379)
  • Mail servers - SMTP (25/587), IMAP (143/993), POP3 (110/995)
  • DNS servers - Port 53
  • Custom services - Any TCP or UDP listener
  • Game servers - Custom port monitoring

Configuration

Host

Enter the hostname or IP address of the service to monitor.

Port

Specify the port number to connect to.

Protocol

Choose between:

  • TCP - Connection-oriented. The check establishes a full TCP connection and considers it successful if the connection is accepted.
  • UDP - Connectionless. The check sends a packet and considers it successful based on the response.

Timeout

Set the maximum time to wait for a connection. If the connection isn’t established within this period, the check is marked as failed.

How It Works

TCP Checks

  1. A TCP connection (SYN, SYN-ACK, ACK) is attempted to the specified host and port
  2. If the connection is established, the check is considered successful
  3. The connection is immediately closed after verification
  4. Connection time is recorded as the response time

UDP Checks

  1. A UDP packet is sent to the specified host and port
  2. The check monitors for a response or ICMP unreachable message
  3. No response within the timeout period may indicate the port is open (UDP is connectionless)

Limitations

  • TCP/UDP checks only verify connectivity, not application-level health
  • UDP checks are inherently less reliable due to the connectionless nature of the protocol
  • Response validation is not available for TCP/UDP checks
  • SSL monitoring is not applicable to TCP/UDP checks
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