Check whether one TCP port is open on a public host or IP, from outside your network
Checked from our server in India. Only the address you type is sent to us; nothing else leaves your device. Updated on 23 Oct 2026.A port checker tries to open a TCP connection to one port of a host from outside your network. This one connects from our server in India, waits up to 5 seconds, and reports open, closed or filtered for 1 port per check, with 20 common ports one tap away.
Type the host name or public IP address, and the port, or pick a common port.
Press Check port. Our server makes one connection, which takes at most 5 seconds.
Read whether the port is open, closed or filtered, then copy the result.
The Port Checker answers one question: can a service on this port be reached from the internet? Our server opens a single TCP connection to the host and port you give it and closes it the moment it opens, without sending anything. Because the attempt comes from outside your own network, it tests exactly what a visitor, a customer or a game client would hit.
There are four possible answers. Open means the handshake completed: something is listening and accepted the connection. Closed means the host answered with a refusal: it is up, but nothing is listening on that port. Filtered means no answer arrived within 5 seconds: a firewall is dropping the attempt, the router has no forwarding rule, or the host is offline. Unreachable means a router on the way reported there is no route.
The usual reason for a forwarded port showing filtered is the forwarding rule itself: the wrong inside address, the wrong protocol, or a second router in front of the first. Some providers block common ports for home connections, and mobile networks behind carrier-grade NAT cannot accept incoming connections at all.
The checker takes one port per request and does not accept ranges or lists: it is meant for checking your own service, not for scanning other people's machines. Only public addresses are accepted, never private ranges, localhost or this site. Each visitor can run 10 checks a minute and 60 an hour across the network tools, and a single host can be checked 20 times a minute in total.
The checker tests TCP only; UDP services such as most game voice chat and DNS over UDP cannot be confirmed this way.
A closed port means the host answered and refused the connection, so the machine is up but nothing listens there. A filtered port means no answer arrived at all within 5 seconds, which usually points to a firewall silently dropping the attempt, a missing router forwarding rule, or a host that is offline.
The most common causes are a forwarding rule pointing at the wrong inside IP address, a firewall on the computer itself, the service not running, or a second router in front of yours. Mobile and some broadband connections use carrier-grade NAT, which cannot accept incoming connections at all.
No. Each check tests exactly one TCP port, and ranges or lists are refused on purpose. The tool exists to confirm that your own service is reachable, not to scan other people's machines, and the per-visitor limit of 10 checks a minute keeps it that way.
No. Our server completes the TCP handshake and closes the connection immediately, without sending a single byte of data. The service on the port sees a connection that opened and closed, which some servers note in their logs.
No, only TCP. A UDP service gives no reply unless it receives a request it understands, so an open UDP port looks the same as a filtered one from outside. Test UDP services, such as voice chat or DNS, with the client software that uses them.
From our server in India. The result shows whether the port can be reached from the public internet at that location. Firewalls that allow only certain countries or addresses can give a different answer to other places, including your own network.
Still stuck? Ask about Port Checker and anybody who knows can answer. No account needed.
Same job, other tools: SRV Record Lookup – Look up SRV records: priority, weight, port and target for a service.
On the related tools: IP to ASN Lookup – Map an IP address to the ASN that announces it, with the BGP prefix.