Master Netcat (nc): The Swiss‑Army Knife for Network Scanning and Communication

nc: The Swiss‑Army Knife of Network Tools

Feature Overview

nc is short for netcat and is renowned as the Swiss‑army knife of networking. Its small size and practical functions make it a simple, reliable tool for various network tasks.

Command Syntax

nc [options] [hostname] [port]

Option Meanings

-g : Set up to 8 router hop gateways.

-G : Set source routing pointer (multiple of 4).

-h : Show online help.

-i : Set interval for sending data or scanning ports.

-l : Listen mode to accept incoming data.

-n : Use numeric IP addresses only, bypass DNS.

-o : Specify a file to dump transmitted data in hexadecimal.

-p : Set the local port to use.

-r : Randomly choose source or destination port.

-s : Set the source IP address for outgoing packets.

-u : Use UDP protocol.

-v : Verbose output showing command execution details.

-w : Set timeout for connections.

-z : Zero‑I/O mode, useful for port scanning only.

Reference Examples

Example 1 – Port Scanning

// Scan TCP ports 1‑1000 on 192.168.154.132
# nc -v -z -w2 192.168.154.132 1-1000

// Scan UDP ports 1‑100 on 192.168.154.132
# nc -u -v -z -w2 192.168.154.132 1-100

Example 2 – Scan Specific Port

# nc -vz -w2 192.168.154.132 22
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 192.168.154.132:22.
Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.