How do I check if a port is open?

Enter the hostname or IP address and the port number, then click Check Port. Our server will attempt a TCP connection to that host and port. An 'open' result means the port is accessible and something is listening. A 'closed' result means either the port is not listening or a firewall is blocking it.

What is port forwarding?

Port forwarding is a router configuration that redirects traffic from an external port to an internal IP address and port on your local network. For example, forwarding port 22 to your home server allows SSH access from outside. Use this tool to verify your port forwarding is working correctly.

Port Checker

Test if TCP ports are open or closed on any host or IP. Verify port forwarding, firewall rules, and server connectivity.

port-check.sh

Host / IP

Port

Testing connection…

common-ports.sh

Host / IP

Scanning ports…

Common TCP Port Numbers

Port	Service	Description
21	FTP	File Transfer Protocol
22	SSH	Secure Shell — remote access
23	Telnet	Unencrypted remote access (insecure)
25	SMTP	Simple Mail Transfer Protocol — sending email
53	DNS	Domain Name System
80	HTTP	Hypertext Transfer Protocol — web traffic
110	POP3	Post Office Protocol — receiving email
143	IMAP	Internet Message Access Protocol — email
443	HTTPS	HTTP Secure — encrypted web traffic
445	SMB	Server Message Block — Windows file sharing
587	SMTP/TLS	SMTP with TLS — modern email submission
993	IMAPS	IMAP over SSL
995	POP3S	POP3 over SSL
3306	MySQL	MySQL database server
3389	RDP	Remote Desktop Protocol — Windows remote access
5432	PostgreSQL	PostgreSQL database server
6379	Redis	Redis in-memory data store
8080	HTTP Alt	Alternative HTTP port — development/proxies
8443	HTTPS Alt	Alternative HTTPS port
27017	MongoDB	MongoDB database server

Frequently Asked Questions

Our server attempts a TCP connection to the specified host and port with a 5-second timeout. If the connection succeeds, the port is marked open. If it times out or is refused, the port is marked closed or filtered. Note: this tests from our server's perspective, not your own network.

Open: a service is actively listening on that port and accepted the connection. Closed: the host responded but no service is running on that port. Filtered/Timeout: a firewall is blocking the connection and not responding at all. A closed port returns a TCP reset; a filtered port just times out.

Set up your port forwarding rule in your router's admin panel, make sure the target service is running on the internal server, then enter your public IP address (found on the IP Lookup page) and the forwarded port number here. If it shows open, port forwarding is working correctly.

Common causes: your firewall (Windows Firewall, iptables, UFW, cloud security groups) is blocking the port; port forwarding is misconfigured on your router; the service is binding to 127.0.0.1 instead of 0.0.0.0; or your ISP is blocking the port (ISPs often block ports 25, 80, and 443 on residential connections).