nc

Additional Notes

nc is a network command used to read and write network connections from the command line. It is a versatile networking Swiss-army knife for port scanning, file transfers, and ad-hoc network connections.

Multiple implementations of nc exist (traditional, OpenBSD, GNU netcat, Nmap ncat). The OpenBSD version is the most common on Linux and does not support the -e flag for security reasons.

Syntax

nc [options] [host] [port]

Parameters

• options: Flags that change how nc behaves.
• host: Hostname or IP address to connect to.
• port: TCP/UDP port number.

Common Options

• -z: Scan without sending data.
• -v: Verbose output.
• -l: Listen for an incoming connection.
• -u: Use UDP.

Examples

nc -zv example.com 443
nc -l 9000
echo test | nc localhost 9000

Practical Notes

nc implementations vary. Some systems provide it as netcat.