Port status checker with service identification. Part of the DevTools Surf developer suite. Browse more tools in the Networking collection.
Use Cases
Identify accidentally exposed database ports (3306, 5432) in development environments.
Verify that a firewall rule correctly blocks specified ports before production deployment.
Check which services are running on a new VPS before hardening it.
Simulate scanning results to understand what an attacker would see from the internet.
Tips
Check common application ports (80, 443, 22, 3306, 5432) first before broad scans to quickly identify exposed services.
Run scans from both inside and outside the network — a port may be blocked externally but open internally, revealing lateral movement risks.
Document every open port with its expected service — unexplained open ports are a red flag.
Fun Facts
Nmap (Network Mapper), the most widely used port scanner, was released by Gordon 'Fyodor' Lyon in 1997 and appeared in multiple Hollywood films including The Matrix Reloaded (2003).
There are 65,535 TCP and 65,535 UDP ports per IP address — a full scan of all ports takes 2–5 minutes with optimized tools.
Port 0 is technically reserved and should never be in use, but receiving traffic on port 0 often indicates a network scanning or OS fingerprinting attempt.
FAQ
Is port scanning legal?
Scanning your own systems is legal. Scanning third-party systems without authorization violates the Computer Fraud and Abuse Act in the US and equivalent laws globally. This tool simulates scanning behavior locally.
What's the difference between TCP and UDP scanning?
TCP scanning completes a handshake (or attempts one) to confirm port state. UDP is connectionless — detecting open UDP ports requires sending application-layer packets and analyzing responses, making it slower and less reliable.
