I have tested the hardware solution based on ESP8266 (ESP-12S) with your code and it was not working. Thanks to your troubleshooting feature I understood why... your endpoints are not exactly the same as ylpk1216's implementation

Your server on kobo expects /left/ and /right/, while the original implementation is expecting /left and /right. I modified the "ino" code to generate the expected endpoints and it works! If you agree I would suggest to fix it in order to keep it compatible.