Port monitoring for the things that don't speak HTTP
Databases, caches, mail servers, message queues, game servers. A TCP monitor opens a connection to host and port on a schedule and tells you when it stops being accepted.
Free for one monitor. No card needed.
What a TCP check actually does
A TCP monitor completes the three-way handshake with your server: it sends SYN, waits for SYN-ACK, replies with ACK, and hangs up. If the handshake completes, the port is open and something is listening. If the connection is refused or times out, it is not. The time between the first packet and the last is the latency you see.
That makes it the right check for anything that is not a web page. Your app might still return 200 while its database is unreachable; a TCP monitor on port 5432 catches that a minute earlier, before the errors pile up in front of customers.
Anything with a port
Type host:port and pick an interval. Hostnames and IP addresses both work, IPv6 in brackets. Each monitor has its own timeout, and a refused connection is reported differently from a silent timeout so you know which one you are dealing with.
- Postgres 5432, MySQL 3306, Redis 6379, RabbitMQ 5672, SMTP 25 or 587, SSH 22
- Custom ports for game servers, VPN endpoints and internal tools you expose
- Private addresses are refused, so a monitor can never scan your own network
When the port stops answering
Set how many failures in a row count as down. Then link the monitor to a status page component and decide what should happen: a status change, a drafted incident, or a published one with subscribers notified.
- A slow handshake shows up as rising latency before it becomes a failure
- Recovery needs the same number of consecutive passes, so a flapping port does not spam anyone
- Every result is kept for 30 days, with daily rollups beyond that
Setting one up
Enter host and port
db.example.com:5432, or [2001:db8::1]:443 for IPv6. No scheme, no path.
Choose interval and timeout
Every minute is a good default for a database. Timeouts default to 10 seconds.
Link a component
Point the monitor at the component your customers would recognise, such as “Database”, and pick the rule.
The other checks
TCP monitoring questions
Watch the port your app depends on.
One monitor and a status page, free. No card needed.