A network port is a 16-bit number (0-65535) that identifies a specific process or service on a device. While an IP address identifies the machine, the port number identifies which application on that machine should receive the data. Think of the IP address as a building's street address and the port as the apartment number.
When a client connects to a server, it specifies both the IP address and port number. Your browser connecting to terminalfeed.io on HTTPS actually connects to the server's IP on port 443. The server listens on that port, accepts the connection, and routes the traffic to the appropriate application. Ports 0-1023 are "well-known" ports assigned to standard services. Ports 1024-49151 are registered ports. Ports 49152-65535 are dynamic/ephemeral ports used for temporary connections.
Common ports: 22 (SSH), 25 (SMTP), 53 (DNS), 80 (HTTP), 443 (HTTPS), 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis), 8080 (HTTP alternate), 27017 (MongoDB). Firewalls control access by allowing or blocking traffic on specific ports.
Port management is a core part of server administration and security. Exposing unnecessary ports increases attack surface. Running services on non-standard ports can provide a thin layer of obscurity (though not real security). Understanding ports is essential for configuring firewalls, debugging connection issues, setting up reverse proxies, and deploying containerized applications where port mapping is a fundamental concept.
TerminalFeed offers a Common Port Reference tool that provides a searchable lookup of standard port numbers and their associated services. The TerminalFeed API runs on standard HTTPS (port 443) through Cloudflare's network.