failed: Error during WebSocket handshake: Unexpected response code: 400

WebSocket connection to 'wss://dev.xxxx.com/socket.io/?EIO=3&transport=websocket' failed: Error during WebSocket handshake: Unexpected response code: 400

using socket.io.
for http it is working fine. but on https://dev.xxxx.com it is not working and showing above error.

any help?
Using CentOS.