The very same name, as well as eventual prefixes, need to be specified in the line of _proxy_pass_.
The very same name, as well as eventual prefixes, need to be specified in the line of _proxy pass_.
The port, in this example set to _3000_, it's the port where Express is mounting the application. By default is 3000, but you can edit it according to the configurations of the express server.
The three `proxy_set_header` Host, Upgrade and Connection are necessary to make the Websocket connection work.