ON Konamiman's website a beta version of Internestor Lite can be found. In december 2002 Néstor Soriano finished his studies with Internestor Suite, a toolkit that allowed any MSX2 with 256kB RAM, DOS2 and an RS232 interface to connect to the internet. Internestor Suite comes with an FTP-client and a telnet client.
However, since it was a university project, when developping it Néstor focused on achieving a modular structure and on complying all the involved standards as strictly as possible, rather than on the usability. As a result, it has three problems: it is too big, too slow, and has too high machine requirements.
The first version of InterNestor Lite adresses these problems. All you need to connect your MSX2 (or higher) to the internet is 128kB RAM, DOS1 or DOS2 and an RS232 interface. This 0.1 version has limited capabilities though. All you can do is open PPP connections and send/receive PINGs.
Relevant link: Internestor Lite