What Is a Port?
Ports are numbered 1–65535 and work over TCP or UDP protocols. Open ports allow your server's services to communicate with the outside world.
Port Check
Check whether ports on a server are open, closed, or filtered. Free port scanning tool.
PORT CHECK
Quick select:
Web:
Email:
Database:
Remote Access:
Port scanning makes TCP connection attempts to the target server. Results are not stored on Secunnix servers.
What Is a Port and Why Does It Matter?
A port is a virtual gateway where specific services communicate on computer networks. Each network connection is identified by an IP address and port number combination.
Security Risk
Unnecessary open ports widen your attack surface. Each open port is a potential entry point; SSH, RDP, and database ports are especially critical.
Port States
Open: service accepting connections. Closed: reachable but no service. Filtered: firewall blocking — the safest state.
Protection Tips
Close unused ports, change the SSH port, close database ports to external access, and perform regular port scans.
What Is a Port and Why Does It Matter?
A port is a virtual gateway where specific services communicate on computer networks. Each network connection is identified by an IP address and port number combination. Ports are numbered 1–65535 and work over TCP or UDP protocols.
Open ports allow your server's services to communicate with the outside world. However, unnecessary open ports create security risks. This tool lets you quickly check port status on any server.
Common Ports and Services
| Port | Protocol | Service | Description |
|---|---|---|---|
| 80 | TCP | HTTP | Websites (unencrypted) |
| 443 | TCP | HTTPS | Websites (SSL/TLS encrypted) |
| 22 | TCP | SSH | Secure remote access and file transfer |
| 21 | TCP | FTP | File transfer (unencrypted) |
| 25 / 587 | TCP | SMTP | Email sending |
| 53 | TCP/UDP | DNS | Domain name resolution |
| 3306 | TCP | MySQL | MySQL database |
| 5432 | TCP | PostgreSQL | PostgreSQL database |
| 3389 | TCP | RDP | Windows Remote Desktop |
| 8080 | TCP | HTTP Alt | Alternative web server, proxy |
Port States: Open, Closed, Filtered
| State | Meaning | Security |
|---|---|---|
| Open | A service is actively accepting connections on this port | Normal for expected services; risky if unnecessary |
| Closed | Port is reachable but no service is listening — connection refused | Generally safe; provides network visibility |
| Filtered | Firewall is blocking packets — no accept or reject response | Safest state; attackers cannot even detect the port |
6 Golden Rules for Port Security
- Close unused ports: Only keep ports you need open in your firewall. Every open port is a potential attack vector.
- Change the SSH port: Moving from default port 22 to a custom port greatly reduces automated brute-force attacks.
- Close database ports externally: MySQL (3306), PostgreSQL (5432), Redis (6379) should never be directly exposed to the internet.
- Review firewall rules regularly: Rules accumulate over time. Audit your firewall rules quarterly.
- Keep port-listening services updated: Software on open ports may contain vulnerabilities. Regular updates are critical.
- Restrict access with VPN: Make remote access ports (SSH, RDP, VNC) accessible only through VPN.
Resources & References
Frequently Asked Questions
What is a port?
A port is a virtual gateway where specific services communicate on computer networks. Each port has a number between 1–65535. Websites typically communicate over port 80 (HTTP) or 443 (HTTPS).
What do open, closed, and filtered mean?
Open: service accepting connections. Closed: reachable but no service listening. Filtered: firewall blocking — no accept or reject response, usually times out.
Do open ports create security risks?
Yes, unnecessary open ports widen your attack surface. Especially SSH (22), RDP (3389), database ports (3306, 5432) are serious risks if exposed externally.
How can I close my ports?
On Windows use Windows Defender Firewall, on Linux use iptables or ufw, on macOS use the built-in firewall. Cloud servers use security group rules.
How does this port check tool work?
Our tool attempts a TCP connection to the specified server and port. If a response is received, the port is open; if refused, closed; if timed out, filtered.
Does VPN affect port checking?
Yes, if using VPN the check goes through the VPN server. To check your own server's ports, enter the real IP address directly.
What are the most common ports?
Most common: 80 (HTTP), 443 (HTTPS), 22 (SSH), 21 (FTP), 25 (SMTP), 53 (DNS), 3306 (MySQL), 5432 (PostgreSQL), 3389 (RDP), 8080 (HTTP alt).
What is port forwarding?
Port forwarding directs traffic from a specific port on your router to a specific device on your local network. Used for home servers, game servers, or remote desktop access.
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