Quickly look up well‑known ports (0–1023) and commonly used registered ports. Includes port number, protocol, service name, description, and security notes. Ideal for system administrators, developers, firewall configuration, and certification prep (CompTIA A+/Network+, CCNA). Expanded with cloud-native & container ports.
| Port | Protocol | Service | Description | Security Notes |
|---|
netstat -ano | findstr :8080 (Windows) / lsof -i :8080 (Linux/macOS)
In computer networking, a port is a virtual endpoint associated with a specific process or service on an operating system. Port numbers range from 0 to 65535 and, combined with an IP address and transport protocol (TCP/UDP), uniquely identify a network communication endpoint. Think of the IP address as the street address of a building, and the port as the specific apartment number.
21, 22, 23, 25, 53, 80, 110, 111, 135, 137-139, 443, 445, 1433, 3306, 3389, 5800, 5900, 8080, 27017, 2375, 9200.
Reference CIS benchmarks and MITRE ATT&CK.
During local development or server deployment you may encounter “port already in use” errors. Quickly identify the offending process with these commands:
To change a service’s default port, edit its configuration file (e.g., /etc/mysql/my.cnf to change 3306) and update firewall rules accordingly.
In May 2017, the WannaCry ransomware spread rapidly across the internet using an exploit (MS17‑010) in the SMBv1 protocol over TCP port 445. Microsoft released an emergency patch, and organizations were advised to block port 445 at the firewall if file sharing was not required. This incident highlights the danger of exposing unnecessary ports and the importance of timely patching and network segmentation.
Misconfigured Docker daemons exposing port 2375 without TLS have led to multiple cryptojacking attacks. Attackers scan for open 2375 and gain root access to the host. Always use TLS (2376) and restrict access with firewalls.