WebSocket is a protocol providing full-duplex communication channels over a single TCP connection. You can read more about WebSockets here. For web applications, we use HTTP or HTTPS protocols with ELB for load sharing. But, AWS ELB with HTTP or HTTPS protocols doesn't support the WebSockets.

How does WebSocket work with load balancer?

The load balancer knows how to upgrade an HTTP connection to a WebSocket connection and once that happens, messages will travel back and forth through a WebSocket tunnel. ... Each client connects to one of your servers, where it then opens a persistent WebSocket connection.

Does NLB support WebSocket?

Network Load Balancer (NLB)

NLB supports long-lived TCP connections that are ideal for WebSocket type of applications.