Port monitoring
Port monitoring for everything that is not a website
Mail servers, databases, SSH, game servers or your own app: Monitorizer opens a TCP connection to the port every minute and tells you when it is refused, times out or gets slow.
- Any port from 1 to 65535
- Checks every minute
- Nothing sent to the service
A simple check that catches a lot
If a service stops accepting connections, everything behind it is down. A port check is the fastest way to know.
Open or closed
An accepted connection is up. Refused, no answer within 10 seconds, or a name that does not resolve is down.
Connection speed
A connection slower than your limit (3 seconds by default) is reported as slow, a common sign of an overloaded host.
Gentle on the service
The connection is opened and closed without sending anything, so it does not fill logs or trigger protections.
Confirmed before alerting
A failed check is tried again a few seconds later before it counts, so a single dropped packet does not raise an alarm.
Common ports to watch
SMTP on 25, 465 or 587 and IMAP on 993, so you know before your clients say email is down.
Databases and caches
MySQL on 3306, PostgreSQL on 5432, Redis on 6379, when they are meant to be reachable.
Your own services
Game servers, VPNs, MQTT brokers, custom APIs: any service that listens on TCP.
Set up in three steps
- 1
Find host and port
For example mail.example.com and 587.
- 2
Add the monitor
Paste host:port in the Mac app, or choose Port on the website.
- 3
Get alerted
When the port is refused, times out or turns slow, and again when it is back.
Every setting, status and tip is in the guide. Open the full guide
Questions
Does it check that the service really works?
It checks that the service accepts connections. For a website, use a website monitor, which also reads the answer, certificate and content. For services on your own server, a server monitor checks that they are running.
Can it watch a port that only my server can reach?
Use a server monitor with “Ports that must listen”: it checks the port from inside the server, over SSH.
Does it support UDP?
No, port monitors use TCP.
Watch the rest of your stack
One app, six kinds of monitors, the same alerts and dashboard for all of them.
- Website monitoringUptime, speed, SSL and hack alerts.
- Status page monitoringKnow when OpenAI, Cloudflare or GitHub is down.
- Server monitoringDisk, memory and services over SSH, no agent.
- Cron job monitoringAlerts when a backup or scheduled job does not run.
- DNS monitoringAlerts when a record changes or a domain is hijacked.
Know the moment a service stops answering
Create your free account in a minute and add your first monitor. Nothing to install on your servers.