The JavaScript test: https://www.mischianti.org/2020/12/07/w ... -client-1/ is using SSL thus it's connecting and handshaking properly with the Tornado server. Whereas your ESP is not setting up SSL and the server is rejecting the connection. It's trying to do strait, unencrypted web sockets. To see if you get the same error, see if your JavaScript version gives the same error if you just do http://www.mischianti.org/2020/12/07/w ... -client-1/
w/ GUI Admin Client, Drag & Drop File Manager, OTA Built-In, Access Point Manager,
Performance Metrics, Web Socket Comms, App API, All running on ESP8266...
Even usable on ESP-01S --- Please check it out!
https://inqonthat.com/inqportal-the-three-line-promise/
https://InqOnThat.com/inqportal