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Monitoring as Code: Learn more about the TCP Monitor Construct.

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What are TCP Monitors?

Use TCP monitors to verify that your non-HTTP services are working as expected. TCP monitors work by establishing a connection to a host and port, then checking the speed and validity of the response. For example, use these checks to verify that:
  • Your mail server is online and responds to IMAPS requests quickly
  • Your FTP server responds correctly to commands
  • Your custom TCP-based service returns the expected response when sent a health check message
TCP monitor interface showing connection status

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How TCP Monitoring Works

TCP monitors perform connection-level checks:
  1. Connection Attempt - Establishes a TCP connection to your service
  2. Port Verification - Confirms the service is listening on the specified port
  3. Response Validation - Optionally validates service responses based on your configured assertions

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TCP Monitor Results

Select a specific check run to review its results:
TCP monitor results page
  • Summary: Displays the monitor target (hostname and port), the monitor state (success for passed and degraded runs, or error for failed runs), the request status code and the total check run duration
  • Error details: If the check failed, the error status code and message log will be shown
  • Request data: If a payload was sent, it is shown alongside the response received from the server
  • Timing phases: For each request, we capture the following timing metrics:
    • DNS: Time taken to resolve the hostname to an IP address (if a hostname was provided)
    • Connect: Time taken to establish the TCP connection (SYN, SYN-ACK, ACK)
    • Data: Time taken to send the payload and receive the response data
Learn more in our documentation on Results.