Port Number

A port number is a 16-bit number from 0 to 65535 that identifies a specific application or service on a computer. While the IP address finds the computer, the port finds the program on it, so one server can run a website, email and a database at the same time on different ports.

Ports 0 to 1023 are well-known ports reserved for standard services. Common ones are 20/21 (FTP), 22 (SSH), 25 (SMTP), 53 (DNS), 80 (HTTP), 443 (HTTPS), 3306 (MySQL), 5432 (PostgreSQL) and 3389 (Remote Desktop). An IP address and port together, such as 192.168.1.5:8080, form a socket.

22    SSH
53    DNS
80    HTTP
443   HTTPS
3306  MySQL
5432  PostgreSQL
6379  Redis
27017 MongoDB