Port Scanner
Scan open ports on your IP address – check which services are accessible from the outside.
Articles related to this tool
How the Port Scanner Works
Our port scanner checks your current public IP address for commonly used and security-critical ports. TCP connection attempts are made to selected ports and the status (open, closed or filtered) is reported back. The test helps you identify unnecessarily exposed services on your network.
Which ports do we check?
We scan the most security-critical and most-abused ports — not all 65,535. A full port scan takes minutes and triggers IDS/IPS alarms. Our selection covers the most important attack vectors:
- 21 (FTP), 23 (Telnet) — unencrypted classics; should no longer be open in 2026.
- 22 (SSH), 3389 (RDP) — popular brute-force targets; if open, then with key auth + Fail2Ban.
- 25 (SMTP), 110 (POP3), 143 (IMAP), 465/587/993/995 — mail servers; only justified for actual mail hosts.
- 80 (HTTP), 443 (HTTPS), 8080/8443 — web servers; expected to be open if you host web services.
- 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis), 27017 (MongoDB) — databases; should never be publicly reachable.
- 53 (DNS), 123 (NTP), 161 (SNMP) — infrastructure services; open ports carry amplification-attack risk.
Open vs. Closed vs. Filtered — what each means
Open: a service answers on the port. Closed: the host is reachable but no service listens on that port (firewall lets the TCP-RST through). Filtered: firewall drops the packet silently — you can't tell if a service is behind it. "Filtered" is better than "Closed" from a security perspective because it hampers port scanning.
Why scan yourself?
Main reason: verify what your router/ISP exposes to the outside. Unintended ports are often open — a smart-home bridge with default login, a Synology NAS with cloud sync, a VoIP router web interface. Server admins also check regularly: does the live state match what was documented? Which ports became newly open after the last upgrade? More background in the article Ports and Firewalls.
What to do about an unexpected open port
First: identify which service is behind it — easiest via SSH/console with `netstat -tulpn` (Linux), or the router web interface under "active connections". Second: check whether the port is intentionally forwarded — default UPnP device rules are common culprits. Third: disable if not needed. Inexplicable open ports may indicate a compromised device.
Frequently Asked Questions about Port Scanner
What are ports and why are they important?
Ports are virtual endpoints for network communication. Each service uses a specific port: e.g. port 80 for HTTP, port 443 for HTTPS, port 22 for SSH. Open ports can be a security risk if unnecessary services are accessible from outside.
Is port scanning legal?
Scanning your own IP address or systems you have permission for is legal. Unauthorised scanning of other systems may be considered preparation for an attack depending on the country. Only use this tool on your own systems or with explicit permission.
What should I do if unexpected ports are open?
Identify the service using the port and check if it is needed. Unnecessary services should be disabled or blocked by firewall. Particularly critical are ports like 21 (FTP), 23 (Telnet) and 3389 (RDP), which are frequent targets of attacks.