Port Checker
Check if a TCP port is open or closed on any host — instant results from Cloudflare’s edge network.
Port Checker in action
You just moved your database to a new server and the app cannot connect. Instead of guessing between firewall, security group, and config, you check port 3306 on the new host: closed. Firewall it is — five minutes saved, one hypothesis tested.
Frequently Asked Questions
How do I check if a port is open?
Enter the hostname and port number, then press Check. The probe opens a TCP connection from a Cloudflare edge server — if the connection succeeds, the port is open. No installation required.
What does an "open port" actually mean?
It means a service on that host is listening on that port and accepted a connection. Open ports are the entry doors of every server — the fewer exposed to the internet, the smaller the attack surface.
Is it safe to check ports on my own server?
Yes. Checking your own server is standard practice — admins verify firewall changes this way all the time. Our checker sends one TCP connection attempt per test, no scans, no data payload.
What is the difference between open, closed, and filtered ports?
Open = a service accepted the connection. Closed = the host answered "nothing here" (RST). Filtered = no answer at all, usually a firewall silently dropping packets. Our result shows open, closed, or timeout (likely filtered).
Which ports should I check after setting up a server?
The ones your service needs: 22 (SSH), 80/443 (web), 3306 (MySQL), 5432 (PostgreSQL), 3389 (RDP). Verify each is reachable, then confirm everything else you are not using shows closed — that is a healthy setup.
How do I check if a port is open for free?
Type the host and port here and press Check Port. No registration, no limits, no command line. The connection test runs from a Cloudflare edge server near you.
Why does the test say closed when my service is running?
Usually a firewall or security group blocks the port, or the service listens only on localhost (127.0.0.1). Rebind the service to 0.0.0.0, open the port in your firewall, and test again.
Can I check ports on another website or server?
Yes — any public host. Checking your own infrastructure is always fine. Checking third-party services is fine for occasional diagnostics, but repeated scanning of someone else’s server is abusive; keep it to single, legitimate checks.