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Netcat (nc) Command Guide

netcat or nc is a powerful command-line tool used for reading and writing network connections. It can perform various network tasks such as creating and receiving TCP or UDP connections, hence it is often referred to as the 'Swiss army knife of networking'. It is very useful for network debugging and management, including port scanning, file transfer, and building simple web servers.

Main Options

`netcat` can perform various functions by combining different options. Use the options below to conduct network tests and transfer data.

1. Connection Mode

2. File and Data Handling

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Description:

`netcat` Executes the command.

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Installing Netcat (nc)

`netcat` is either installed by default on most Linux systems or provided as a symbolic link named `nc`. If it is not installed, you can easily install it using the commands below.

Debian/Ubuntu

sudo apt update
sudo apt install netcat

How to install netcat on Debian or Ubuntu based systems.

CentOS/RHEL/Fedora

sudo yum install nc

How to install netcat on CentOS, RHEL, or Fedora based systems.

Arch Linux

sudo pacman -S openbsd-netcat

How to install netcat on Arch Linux.

Commonly Used Examples

Learn various uses of `netcat`. It can be used for checking network ports, transferring files, and building simple chat servers.

Check if a Specific Port is Open

nc -vz example.com 80

Checks if port 80 (HTTP) on example.com is open. Returns 0 on successful connection.

Using as a File Server

nc -l -p 12345 < filename.txt

Sets up a simple server to send a local file to clients on port 12345. Clients can receive the file using the command `nc [serverIP] 12345 > received_file.txt`.

Using as a File Client

nc [serverIP] 12345 < filename.txt

Receives a file on port 12345 from the server. The server must execute the command `nc -l -p 12345 > received_file.txt`.

Building a Simple Chat Server

nc -l -p 8888

Opens a simple chat server on port 8888 on the localhost. Multiple clients can connect to this port to communicate with each other. The `-k` option can be added to keep the connection alive.

Additional Tips

nc command can also be executed as netcat depending on the distribution. Check for symbolic links or see detailed usage with man nc or man netcat commands.

  • nc vs netcat: On most systems, nc is a symbolic link to netcat. Some systems may differentiate between packages like netcat-traditional and netcat-openbsd.

Related commands

These are commands that are functionally similar or are commonly used together.

ping

ping Command Guide: Checking Network Connectivity

ssh

SSH (Secure Shell) Command Guide

telnet

Complete Guide to the Telnet Command

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