问题
I have an aws application load balancer with an https listener on port 9999, forwarding to a group on port 9999 with an ec2-instance being the target.
If I run my websocket server with the host name configured to my domain api.example.com, then when the client tries to open a websocket connection it gets:
Error during WebSocket handshake: Unexpected response code: 502
However, if I configure my websocket server with an empty string instead of the domain, then it connects just fine!
This is problematic because the server I am intending to run on this instance automatically launches a websocket server ONLY IF there is a websocket host name configuration provided, so a blank string means the websocket server will never launch! I would prefer to not have to hack the library to get around that condition. So I am wondering, why in the world a blank string works, but the domain name does not?
I tried localhost, the ip of the box, etc, everything results in a 502 except a blank string!
来源：https://stackoverflow.com/questions/51053863/websocket-server-host-has-to-be-blank-in-order-to-work-on-ec2-instance-with-appl