This also matters for load balancers. With SSE or chunked encoding long polling, it's possible to lose the client connection without the load balancer closing t

This also matters for load balancers. With SSE or chunked encoding long polling, it's possible to lose the client connection without the load balancer closing the connection to the server, at least for a while. WebSockets make it easy to do periodic heartbeats from the server, which puts an upper bound on how long a client connection can be in an uncertain state. This also enables client presence data, even if the client only ever receives messages.