TCP port monitoring
A connection opened to a host and port every minute. Refused or timed out is down; the time to connect is the response time on the strip.
Northwind is up.
The monitor is responding, 2 failed checks in the last 24 hours.
Postgres, port 5432
Up for 5 h 44 min99.86% passed
1,438 checks, median 14 ms, 2 failed checks
95% under 20 ms
- Failed2 min, 2 checks
How the check works
A TCP monitor opens a connection to the host and port you name, then closes it again. Nothing is sent. The check passes when the connection is accepted within the ten-second timeout and fails when it is refused, unreachable, or times out. The response time recorded is the time to connect, so the strip shows a database that is accepting connections slowly before it stops accepting them at all, and a slow threshold puts a figure on that.
Use it for anything that is not HTTP: a Postgres or MySQL port, an SMTP or IMAP server, SSH on a box that should always answer, a game server, a message broker. For a service that does speak HTTP a website monitor tells you more, since it also reads the status and the body. Checks run from public addresses, so the port has to be reachable from the internet; for a service behind a firewall, a heartbeat pinged from inside does the job.
When it counts as down
A port monitor counts as down after two failed checks in a row and as back after one success. Before a failure counts, it is checked again in the same region; only a failure both checks see goes on the record. On Hobby and Pro every other region checks at the same moment, so the page can say down from North America instead of down. A single failed check still appears on the strip with its time and reason, it just does not change the state or send an alert.
Alerts
Each change of state sends one alert: down, and back, with how long it was out. Email is on every plan. Hobby and Pro add Slack, Discord, Microsoft Teams, Telegram, PagerDuty, Opsgenie, Pushover, ntfy and a signed webhook, plus a repeat notice every so many minutes while an outage lasts. Nothing is sent during a maintenance window.
What the status page shows
Every port monitor gets a strip on the public page. Each bar is one check, its height the response time; amber marks a timeout and red any other failure. Consecutive failures are grouped into one entry with the time and the reason, and the mark stays there for the whole range. A port monitor going down opens an incident on the page by itself and resolves it on recovery.