It seams that "Code in ASP (VB) (demo_sse.asp)" block needs correction in the article HTML5 Server-Sent Events.
Original string does not return data to client browser:
Response.Write("data: The server time is: " & now())
Line feeds ("\n\n")are missing. This works:
Response.Write("data: The server time is: " & now() & vbLF & vbLF)