Open port checker
See whether a TCP port accepts connections from BuildSpace—useful after changing firewalls, load balancers, or security groups.
What an open-port check is for
Firewall rules, security groups, and upstream ISPs determine whether a TCP port accepts connections from the wider internet. Operators ask: “Is 443 reachable from outside?” “Did my DB port accidentally become public?”
This tool attempts a TCP connect from BuildSpace to your host and port. A successful handshake suggests the port is open to us; failure can mean closed, filtered, or rate-limited—interpret alongside your cloud console.
It complements application-level checks (HTTP headers, TLS) when you are debugging connectivity layers.
How this tool works
Short technical summary of what runs on our servers when you click the button.
We try to complete a TCP connection with a timeout. No application protocol is spoken beyond the handshake.
If the port accepts the connection, we record how long setup took from our side.
We refuse private and reserved destinations so the feature cannot be used to map internal networks.
More BuildSpace tools
All utilities run from our infrastructure with the same safety limits. No account required.
- Site statusSee if a URL responds from our servers—outage vs. local issue.
- DNS lookupA, AAAA, MX, CNAME, TXT, and NS records for a domain.
- HTTP header checkerStatus code, full response headers, and common security headers.
- SSL certificate checkerCertificate subject, issuer, validity, fingerprint, and SANs.
- Ping & response timeThree-run DNS, TCP, and HTTP timing breakdown (no ICMP).
- WHOIS (RDAP)Registrar and registration data via RDAP where available.
- Website speed testTTFB, sampled bytes, Content-Length, and encoding hints.