Which is my point, the right tool in that case is one that fit on the memory footprint of an embedded microcontroler.
> On porting libraries...well, the WebSockets client I play with is only 60 lines.
Theses 60 lines does almost nothing. You ignore the 240 lines inside protocol.py just beside. You also ignore the 600 KB binary required for MicroPython. Already you simply CAN'T run on an ESP8266 that's only embedded with 512 KB (so can't be run on any of my ESP-01 module).
That does make me think though that the Websocket protocol is quite simpler than I though, but if I were to use it, I would plainly do a socket connection instead which would be even more simple.
> I use the D1 mini :)
Sure with one big enough, but we are talking about embedded, where resources are scarce. Running Micropython is a luxury for many embedded developers.