Check If a Port Is Open
Need to check if a port is open? Whether you're a developer debugging a firewall rule, a sysadmin verifying a service is running, or a security professional auditing your attack surface — VulnScan's port tester gives you an instant answer from any browser.
Related Port Scanning Tools
Common Ports & Their Security Risk
| Port | Service | Risk Level | Notes |
|---|---|---|---|
| 22 | SSH | ⚠️ Medium | OK if needed, restrict to known IPs |
| 23 | Telnet | 🔴 Critical | Unencrypted — disable immediately |
| 80 | HTTP | 🟢 Low | Expected for web servers |
| 443 | HTTPS | 🟢 Low | Expected — ensure TLS is current |
| 3306 | MySQL | 🔴 Critical | Database — never expose to internet |
| 3389 | RDP | 🔴 Critical | Most attacked port on internet |
| 5432 | PostgreSQL | 🔴 Critical | Database — close or firewall |
| 6379 | Redis | 🔴 Critical | Often exposed without auth — check now |
| 27017 | MongoDB | 🔴 Critical | Leaked millions of records historically |
| 8080 | HTTP Alt | ⚠️ Medium | Dev servers often exposed accidentally |
Frequently Asked Questions
Why would a port show as filtered instead of closed?
"Filtered" means a firewall is blocking the scan probe — the port may or may not be open behind the firewall. "Closed" means the port is reachable but no service is listening. "Open" means a service is actively accepting connections.
How can I open a blocked port?
To open a port on a server: configure your firewall (iptables, ufw, AWS Security Groups, etc.) to allow inbound traffic on that port, and ensure the service is running and bound to that port. Consult your hosting provider's documentation for specific steps.
What is the difference between TCP and UDP ports?
TCP ports require a confirmed handshake — they are reliable and used for web (80/443), SSH (22), databases. UDP ports are connectionless — faster but unreliable, used for DNS (53), VoIP, gaming. Most web security scans focus on TCP ports.