How to check which TCP ports are open on a host

1. Enter the target host

   Type a hostname or public IPv4/IPv6 into the "Host or IP" field. Up to 253 characters. Private addresses (10.x, 192.168.x, etc.) and localhost are rejected.

2. Tick the common ports you want

   The form lists labelled checkboxes for the usual suspects (22 SSH, 25 SMTP, 80 HTTP, 443 HTTPS, 3306 MySQL, 5432 Postgres, 6379 Redis, etc.). Tick all the ports you want to probe.

3. Add custom ports (optional)

   "Custom ports" accepts a comma- or space-separated list of additional ports (1–65535). Example: 27017, 9090. Up to 40 ports total per run, including ticked common ones.

4. Press Run and read results

   Each requested port returns { port, open }: open=true means a TCP socket succeeded within 4s. Closed could mean filtered or genuinely closed — port scanning is best-effort and may be blocked by upstream firewalls.