[Python] FastAPI (Python) Why I get "Unsupported upgrade request." with POST request?

I have similar apps on Flask and FastAPI. When I do this curl requests with Flask, that is all right:

Without TLS:

curl -X POST -H "Content-Type: application/json" -d '{"method": "account.auth"}' http://X.X.X.X:5050/

{"error":0,"result":{"token":"XXX"}}


With TLS:

curl -X POST -H "Content-Type: application/json" -d '{"method": "account.auth"}' https://example.com:8443/api/

{"error":0,"result":{"token":"XXX"}}


!!! But with FastAPI I get another result:

Without TLS:

curl -X POST -H "Content-Type: application/json" -d '{"method": "account.auth"}' http://X.X.X.X:5050/

{"error":0,"result":{"token":"XXX"}}


With TLS:

curl -X POST -H "Content-Type: application/json" -d '{"method": "account.auth"}' https://example.com:8443/api/

Unsupported upgrade request.


How to fix problem with "Unsupported upgrade request."? And what is it? Flask are working with it normally.

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