Port checker
Enter a host and one port. Each of our 15 locations tries to open a TCP connection to it and tells you whether it got through and how long it took.
Common: 22 SSH · 25 SMTP · 80 HTTP · 443 HTTPS · 3306 MySQL · 5432 PostgreSQL · 3389 RDP
Want to know when it stops answering?
Monitor the port from the same 15 locations. 650,000 free credits every month.
What is a port checker?
A port is a numbered door on a server: 443 for HTTPS, 22 for SSH, 25 for email, 3306 for MySQL. A port checker tries to open one from the outside. «Open» means something is listening and the firewall lets it through; «closed» or «timed out» means it doesn’t, from that location.
One connection from each of 15 places.
At the same second, each of our 15 probes on 6 continents opens one TCP connection to the port and closes it again. Nothing is sent over it. «Connect» is how long the handshake took, about one round trip, so it grows with distance. A firewall that answers some networks and not others shows up as a mixed result.
Never a range
One port per check, and one check per host per minute, so the tool can’t scan anyone.
Handshake only
We open the connection and close it. No data, no login attempts.
Locations
Europe, the Americas, Asia, Oceania and Africa, on five providers.
Internet only
Private and reserved addresses are refused. Owners can ask us not to check their hosts.
Why one port at a time?
So the tool can’t be used to scan other people’s servers. Checking one port you run is enough to answer the question.
Can I check my home network?
Yes, using your public IP address. Private addresses (192.168.x.x, 10.x.x.x) can’t be reached from the internet and are refused.
Does open mean safe?
No, only reachable. Keep open only the ports you need, and protect admin ports like SSH with keys and an allow-list.
Do you check UDP?
No, TCP only.
Why do some locations say «not tested» for mail ports?
Some hosting providers block outgoing mail connections to stop spam. Port 25 can be tested from 10 of our 15 locations; the other five, on DigitalOcean, InterServer and Melbicom, can’t reach it, and the DigitalOcean ones can’t reach 465 and 587 either. Those locations tell you nothing about your mail server, so we leave them out and judge from the ones that can.
Do you store what I check?
The address, the results and your IP are kept for 7 days, so the result link can be shared. Nothing else.