Glossary · Types of monitoring
Port monitoring checks that a service accepts TCP connections on a given port, such as 22 for SSH, 25 for SMTP, 443 for HTTPS or 5432 for PostgreSQL, and alerts when a connection can’t be opened.
A TCP check completes the three-way handshake (RFC 9293) and closes the connection. Success means something is listening and reachable through every firewall on the way; it doesn’t prove that the service behind it answers correctly.
Use it for services that don’t speak HTTP: mail servers, databases, game servers, SSH, message brokers and custom protocols. For web services, an HTTP check tests more.
IANA divides ports into system ports (0–1023), user ports (1024–49151) and dynamic ports (49152–65535), as described in RFC 6335. Opening a database port to the whole internet only to monitor it is a risk; allow the monitor’s addresses instead.
Uptimecheck port monitors open a TCP connection to a host and port as often as every minute, with a timeout from 1 to 30 seconds (10 by default), and record how long the connection took. A failure is confirmed by a second check before anyone is alerted.
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A practical guide to server monitoring: which metrics to track, how to set useful alerts, how to read logs and how to fix the most common server problems.
ReadPing tests that the host is reachable over ICMP. A port check tests that a specific service is listening and reachable over TCP, which is closer to what its clients do.
UDP has no handshake, so a simple connection test can’t tell an open port from a filtered one; it needs a request in the service’s own protocol. Uptimecheck’s port monitors check TCP.
Open it only to the monitor’s IP addresses, not to everyone. For databases, a health check endpoint in your application is often the safer thing to monitor.
Set up your first monitor in under a minute, or look around the live demo first.
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