TL;DR

Netcat is a mess.

Netcat is a fantastic tool. You don’t have to trust me… just read Wikipedia on netcat:

netcat (often abbreviated to nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP. The command is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and investigation tool, since it can produce almost any kind of connection its user could need and has a number of built-in capabilities.

But… there’s more than one contender in town, and different implementation can have wildly differing features.

The Ports and reimplementations section basically says it all. On a more practical note:

• the version that comes with busybox is really simple
• the GNU netcat has a wider feature set, but lacks support for using proxies;
• the BSD netcat is more evolved, and supports proxies through the -x and -X options;
• the Nmap netcat (a.k.a. ncat) is another alternative that is feature-packed, including support for proxies, although with different options (--proxy and --proxy-type).

So here we go, there’s a lot of hints around the Internet… but we get to know which alternative they’re talking about!