[Victor Trucco] makes us wish we spoke Portuguese. He’s done a lot of retrocomputing projects including connecting a ZX81 to the Internet to load programs. The project uses — what else — an ESP8266 to get the WiFi communications. You can see a video below if you want to exercise your high school Portuguese.
It is somewhat ironic that the ZX81’s CPU is kept busy driving the video, reading the keyboard, and running about just over 3 MHz which doesn’t even translate into 3 MIPS on that processor. Meanwhile, the “servant” ESP8266 has a 32-bit Tensilica CPU running at 80 MHz. Times have changed.
The interface presents a control web page for configuration via a normal PC or other Web-browser capable device. The ZX81 uses the LOAD command to interact with a remote FTP server. The reference to TK85 in the video is apparently a Brazillian ZX81 clone.
You can spend a lot of time on [Trucco’s] site wrestling with Google translate. We’ve seen some TK85 hacks before. We’ve also covered some of [Trucco’s] work on the Atari (although the link in that post has moved).