Junior
On which ports can you see current connections in the LISTENING state?
sobes.tech AI
Answer from AI
# View all LISTENING ports with process information
sudo netstat -tulnp | grep LISTEN
# View all LISTENING ports with process information (alternative with ss)
sudo ss -tulnp | grep LISTEN
Main ports and protocols where LISTENING connections are commonly found:
| Protocol | Port | Description |
|---|---|---|
| TCP | 22 | SSH (Secure Shell) |
| TCP | 80 | HTTP (Hypertext Transfer Protocol) |
| TCP | 443 | HTTPS (HTTP Secure) |
| TCP | 25 | SMTP (Simple Mail Transfer Protocol) |
| TCP | 5432 | PostgreSQL Database Server |
| TCP | 3306 | MySQL Database Server |
| TCP | 6379 | Redis |
| TCP | 27017 | MongoDB |
The netstat and ss commands display information about current network connections and listening ports. Flags -t (TCP), -u (UDP), -l (LISTENING), -n (numeric addresses), -p (process) are used for filtering and displaying the needed information. grep LISTEN filters lines containing the word "LISTEN", indicating ports in the listening state for incoming connections.