September 7, 2026 · Yunus Emre Vurgun
Common Network Ports Reference
Eleven ports cover the services developers touch daily: web, SSH, DNS, mail, and the four database defaults. Memorize the table and firewall rules, connection strings, and "connection refused" errors get much easier to read.
The ports
| Port | Protocol | Service | What it is |
|---|---|---|---|
| 21 | TCP | FTP | File Transfer Protocol — unencrypted file transfers. |
| 22 | TCP | SSH | Secure Shell — encrypted remote access. |
| 25 | TCP | SMTP | Simple Mail Transfer Protocol — email routing. |
| 53 | TCP/UDP | DNS | Domain Name System — hostname to IP resolution. |
| 80 | TCP | HTTP | Hypertext Transfer Protocol — unencrypted web traffic. |
| 443 | TCP | HTTPS | HTTP over TLS — encrypted web traffic. |
| 3306 | TCP | MySQL | MySQL database server — default port. |
| 5432 | TCP | PostgreSQL | PostgreSQL database server — default port. |
| 6379 | TCP | Redis | Redis in-memory data store — default port. |
| 8080 | TCP | HTTP Alt | Common alternate port for HTTP proxies and dev servers. |
| 27017 | TCP | MongoDB | MongoDB default port for standalone and replica set nodes. |
Reading "connection refused"
That error with a port number tells you exactly which row of this table to check: nothing is listening there. The usual causes in order are the service isn't running, it is bound to localhost instead of the external interface, or a firewall drops the packets. Match the port to the service first — 5432 means Postgres, 6379 means Redis — and you start debugging the right process instead of the network in general.
Fetch it as data
This table is the Network Ports Reference dataset:
curl "https://yjtoon.com/api/dataset/network-ports-reference?format=toon"Go deeper with TCP/IP Protocol Suite, OSI Model Layers, and DNS Fundamentals.