Linux Command - nc
nc - Netcat utility
Syntax
1 | nc [options] host port |
Description
Netcat is one of the most powerful networking tools, security tools, and network monitoring tools.
It can be used for
- Network debugging tool
- Port scan
- Port listening
Options
| Option | Description |
|---|---|
| -l | Listen mode, used to create a server that listens for incoming connections. |
| -n | disable DNS lookup to avoid delays |
| -n, –no-clobber | do not override existing file |
| -v, –verbose | verbose mode, provides more details |
| -z | Scans for open ports. |
Example
Check if port is open
check if github.com port 443 is open
1 | nc -vz github.com 443 |
output
1 | Connection to github.com port 443 [tcp/https] succeeded! |
You can also use IP address instead of hostname
1 | nc -vz 140.82.112.3 443 |
Port Scanning
Port scanning is a common technique to discover open ports. It can be considered hostile. Please only use it on your own hosts.
Scan port 1 to 100
1 | nc -vz localhost 1-100 2>&1 | grep succeeded |
Listen to incoming connection
1 | nc -l 4000 |