Author: Sahil Suri

  The Linux netcat(nc) command is often referred to as the Swiss army knife of networking tools, and a skilled system administrator could come up with some interesting uses for this sophisticated and versatile tool. It essentially establishes a connection between two computers and allows data to be written across the TCP and UDP transport layer protocols, and the network layer protocol IP. Netcat could even be thought of like the ‘cat’ command in Linux but for network-based communication between servers. Netcat operates in 2 modes Server mode Client mode Server mode: In the server, mode netcat listens to incoming connections depending on various parameters that may have been passed to the utility.The below syntax indicates how you would typically use netcat in the server mode: nc -l -p port [options] [hostname] [port] Client mode: In the client, mode netcat initiates a TCP/UDP connection to the same or different machine.The below syntax depicts how you would typically use netcat in the client mode: nc [-options] hostname port[s] [ports] We will be covering both methods in depth in our examples. Typical uses of the Linux netcat tool Chat server Port scanner File transfer Information fetching Chat server: We can use netcat to transfer simple text messages between two system forming a rather minimal and straightforward instant messaging interface. Port scanner: Netcat can be used to scan open ports on one or more systems. Its...