TCP port checks

A TCP port check connects to a port on a host and alerts when the connection fails.

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Adding a TCP port check

In Add check, choose Host doesn’t respond at a TCP port under Alert us when…, then fill in Host to monitor and TCP port (1–65535). If you type host:port into the host field, the port is filled in for you. If you leave the name blank, the check is named host:port.

Watching a TLS certificate

For a TLS service, such as HTTPS, turn on Use TLS and watch the certificate. It’s off by default. With it on, the check also opens a TLS connection and verifies the certificate against the host you entered, and it warns before the certificate expires, at 21, 14, and 7 days. The days left also show on the check’s card.

Self-signed certificates fail

With TLS on, an invalid, expired, self-signed, or mismatched certificate makes the check down, with the message “TLS connection failed: …”. Port checks can’t skip verification, so leave TLS off for servers with self-signed certificates, which many VPN servers use.

Check frequency, the confirmation period, and the request timeout are described in Working with checks.