What is a port check?
A port check tests whether specific TCP ports on a host are accepting connections. This port check tests connectivity to a fixed list of well-known TCP ports — web, mail, SSH, databases and more — and reports which are open. The port list is fixed and private addresses are blocked, so it cannot be used to scan internal networks.
How a TCP port check works
A port is a numbered endpoint a server uses to separate different services on one IP address. The check attempts a TCP connection to each port in its list and watches the result: if the handshake completes, the port is open and a service is listening; if the connection is refused or times out, it is reported as closed or filtered. IPeek tests a fixed set of well-known ports such as 80 and 443 for web, 22 for SSH, 25 for mail and 3306 for MySQL, so you see which standard services a host exposes.
Open versus closed and filtered ports
An open port completed the TCP handshake, meaning a service is actively listening and reachable. A closed port refused the connection: the host answered, but nothing is listening there. A filtered port gave no answer at all, usually because a firewall silently dropped the packet, so the check times out without a definitive refusal. The practical difference matters: a closed port tells you the service simply is not running, while a filtered port tells you something is deliberately blocking access before the request ever reaches the service.
What common open ports tell you
Each well-known port maps to a service, so the open list is a quick inventory of what a host runs. 80 and 443 mean a web server; 22 means SSH for remote administration; 25, 465 and 587 relate to email submission and transport; 3306 is MySQL and 5432 is PostgreSQL. Seeing a database port open to the public internet is usually a red flag, since databases should sit behind a firewall. Use the results to confirm the services you expect are reachable and to spot anything exposed that should not be.
Why this tool will not scan internal networks
This check is deliberately limited so it cannot be misused for reconnaissance. The port list is fixed rather than user-chosen, so you cannot sweep arbitrary ranges, and requests to private and reserved address ranges are blocked outright. That means you cannot point it at internal hosts like 192.168.x.x or 10.x.x.x to map a network you do not control. The tool answers a narrow, legitimate question — which standard public services is this host exposing — without becoming a general-purpose network scanner.