Port Checker
Test whether a TCP port is open on any host. Useful for verifying firewall rules or external service reachability.
Port 443: HTTPS
A raw TCP connection is attempted from our server.
Select a common port or enter a custom one
Open, closed, filtered, or timeout status appears here.
Port Checker attempts a raw TCP connection to a specific port on a server from an external vantage point and reports whether the port is open, closed, or filtered. This answers a narrower question than a general uptime check: whether a specific service on a specific port is reachable from outside the network.
Open indicates that a service accepted the connection. Closed indicates that the host responded, but no service is listening on that port. Filtered, or a timeout, typically indicates that a firewall or security group is silently dropping the connection attempt rather than rejecting it outright — the most common cause of a port that should be open but does not connect.
This method is typically the fastest way to isolate a firewall or NAT misconfiguration from an application-level problem. If the port itself does not connect, the service behind it cannot be evaluated until connectivity is restored.