[drothlis]

Same way that if you make 2 "normal" GETs simultaneously to the same server the responses don't get mixed up, i.e. they'll be separate HTTP Connections which are separate TCP connections:

> Each HTTP connection maps to one underlying transport connection.

-- https://httpwg.org/http-core/draft-ietf-httpbis-messaging-la...

TCP uses "port numbers" to identify different connections. 2 different connections from your PC to the same web server will use 2 different "source" ports. A port is just a number in the TCP header. https://en.wikipedia.org/wiki/Transmission_Control_Protocol#...

HTTP/1.1 added pipelining, so you can make several requests on the same TCP connection before receiving a response. But the (complete) responses must arrive in the same order of the requests so it doesn't work for SSE.

HTTP/2 added request & response multiplexing on the same TCP connection. But (according to the OP) there are some limitations that affect SSE.