Websocket endpoint issue

[shenbagapandian]

If my endpoint like this http://domain_url:4000/graphql, then everything working fine.
And i changed my endpoint to http://domain_url/graphql then i'm facing issue like : "Could not connect to websocket endpoint ws://domain_url/graphql. Please check if the endpoint url is correct." . I'm using centOS for reverse proxy. Is anything needed for graphql subscription ?? kindly guide me for the subscription server setup .