Port Checker — Test if a TCP or UDP Port is Open
Find out in 3 seconds whether a TCP or UDP port is reachable from the public internet on any IP address or hostname.
Our port checker connects from external infrastructure (not your local network), so the result reflects what an outsider — or a botnet — would actually see. Use it to verify firewall rules after a deployment, debug why an SMTP/MySQL/Minecraft server is unreachable, confirm port-forwarding on a home router, or audit your VPS for accidentally exposed services. Supports the full 1–65535 range plus quick presets for HTTP (80), HTTPS (443), SSH (22), RDP (3389), FTP (21), MySQL (3306), PostgreSQL (5432), Redis (6379), MongoDB (27017) and 30+ common services.
Port Checker is a free online tool to check TCP port availability on remote hosts and IP addresses. Our port scanner helps system administrators, developers, and security professionals quickly diagnose network connectivity issues.
Common ports and their purposes:
- Port 80 (HTTP) - Unencrypted web server
- Port 443 (HTTPS) - Secure web server
- Port 22 (SSH) - Remote SSH access
- Port 21 (FTP) - File transfer
- Port 25 (SMTP) - Email sending
- Port 3306 (MySQL) - MySQL database
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Port Checker - Online Open Port Check Tool
Port Checker is a professional tool for network diagnostics. Check if TCP/UDP ports are open on any server in seconds. Essential for firewall configuration, server setup, and network security.
Common Ports
- 80/443 - HTTP/HTTPS (web server)
- 22 - SSH (remote access)
- 3306 - MySQL (database)
- 3389 - RDP (Remote Desktop)
How to check if a port is open
- Set the host — IP or domain (my-server.com or 123.45.67.89).
- Enter the port — e.g. 22 for SSH, 443 for HTTPS, 25565 for Minecraft.
- Run the check — our server tries to establish a TCP connection from the public cloud — the same way a visitor would.
- Read the verdict — "Open" — service reachable from the internet; "Closed" — firewall or NAT blocks it.
Example use cases
Home server check
Opened a port on the router for RDP or a game server? Test from outside before sharing the IP with friends.
Mail server diagnosis
Ports 25, 465 and 587 are often blocked by ISPs. A quick check tells you whether a relay or plan change is needed.
Security audit
Make sure admin ports (3389 RDP, 22 SSH, 3306 MySQL) are closed externally or IP-whitelisted — otherwise bots will find them.
Docker/Kubernetes debugging
App runs in a container but is "unreachable from outside"? A port check isolates firewall from application issues.
Common mistakes & fixes
- Port 80 open but site does not load
- TCP works, but HTTP errors. Check the web server config (Nginx/Apache) and virtual hosts.
- ISP blocks port 25
- Major carriers (Comcast, AT&T, Verizon) filter outbound SMTP. Use 465/587 or order an SMTP relay from your host.
- Port open in Windows Firewall but closed externally
- Behind a NAT router you need port forwarding to the local IP. Check the router admin under Virtual Server / Port Forwarding.
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