It has interesting options such as `-o` which dump a netcat session to a file, `-k` which makes the listening socket accept several connections and `-c` which execute command on incomming connection. DonвЂ™t forget to sudo update-alternatives -config nc to use appropriate implementation.ДЄdditionnaly, you have a similar tool named `ncat` which comes from `nmap` project. On Ubuntu, both versions exists with packages netcat-openbsd and netcat-traditional. Use `nc -h` to know which version you use and what does the options do. Netcat is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts. Knowing which implementation of netcat you use is important several options are behaving differently. Netcat (nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP. Examples in this article assumes you have openbsd netcat. Possible issues Which flavor of netcat?!ДЄlright, netcat has different implementations, namely openbsd and gnu. If you have difficulties wrapping your head around it, try playing with individual commands like nc, tee, read about unix pipes and named pipes. Note that we write back server response to the answer named pipe.Д®verything from the first nc is chained through unix pipes | which redirects content of left hand side stdout to right hand side stdin. Tee -a out answer: You know what tee does now. The script expects the BSD version, but it could be made to work with the GNU version with a minor change. Stdin here being HTTP request content which is chained up until here. Also, there are incompatible versions of netcat (BSD vs GNU) out there, so maybe that is part of the issue. Server response is then written on stdout. the original the BSD implementation The idea is the same but some behaviour differs, e.g. It is designed to be a reliable 'back-end' tool that can be used directly or easily driven by other programs and scripts. There are two distinct things called netcat. Implicitly tee will also print to stdoutД¬onnects to on port 80 and write stdin content on the socket. Netcat is a featured networking utility which reads and writes data across network connections, using the TCP/IP protocol. Stdin here being content of HTTP requests, it will write it to in file and to /dev/fd/2 (which is stderr, to see request content in console). Tee will read stdin to write back to stdout and files in parameters. k enable netcat to continue listening after connection close (netcat can accept several successive connections) It listens to tcp port 8001, then reads value of named pipe answer to send it back to the client. Netcat 2 in listen mode will print incomming request content to stdout and send stdin back to client. Touch in out: Create files named in and out, respectively for persisting the streams of incoming request and outgoing responses. In essence the same thing than the regular unix pipe |, except it exists on the filesystem thus you reference it by its name. And not all options from OpenBSD-netcat have all other versions and vice versa.Д«esides, it possible to get almost same functionality with just bash and named pipes using it pseudo-interface /dev/tcp, in reverse mode.Nc -vv -l -k -p 8001

Gnu netcat vs bsd netcat