These two lines of configuration are used when configuring a reverse proxy server to handle WebSocket connections.
The first line proxy_set_header Upgrade $http_upgrade; tells the NGINX server to pass along any upgrade requests from the client to the backend server. In this case, it’s looking for an HTTP header called “Upgrade” and passing along its value.
The second line proxy_set_header Connection "upgrade"; tells NGINX to change the connection header to “upgrade” so that it can properly handle WebSocket connections between the client and backend server.
Together, these lines ensure that NGINX can properly upgrade an HTTP connection to a WebSocket connection and allow bidirectional communication between the client and server.
