What is the Remote TCP Port Scanner?
A server-side scanner that tries to open a TCP connection to a list of commonly used ports on a target host, then reports which ones answered, refused, or timed out.
How it works
The scan runs on the server with Node's net.Socket module: for each port (18 common ones by default, like SSH 22 and MySQL 3306, or a single custom port you specify) it opens a TCP socket and waits up to 3-4 seconds. A successful connect means the port is open, an immediate refusal means it's closed, and no response before the timeout means a firewall likely dropped the packet. The target is checked against a private/internal-address guard before scanning so the server can't be used to probe its own network.
SysAdmin & security use cases
- Checking whether a database port like 3306 or 5432 is accidentally exposed to the public internet
- Confirming a firewall rule change actually closed a port after deployment
- Spot-checking a new cloud VM for services left running from a default image
- Testing whether a specific non-standard port used by an internal app responds from outside the network