Question

From this article on Wikipedia:

Keepalive messages were not officially
supported in HTTP 1.0. In HTTP 1.1 all
connections are considered persistent,
unless declared otherwise.

• Does this mean that using this
  mechanism I can actually simulate a
  TCP socket connection?
• Using this can I make a Server
  “push” data to a client?
• Are all HTTP connections, even the
  one I am using to connect to Stack
  Overflow “HTTP persistent”?
• Does the COMET technology of
  server push use this mechanism of
  HTTP persistent connection to push
  data to clients?

Answer 1

• Does this mean that using this mechanism I can actually simulate a
  TCP socket connection?

Not really, sockets have MANY more features and flexibility.

• Using this can I make a Server “push” data to a client?

Not directly, it’s still a request/response protocol; the persistent connection just means the client can use the same underlying socket to send multiple requests and receive the respective responses.

• Are all HTTP connections, even the one I am using to connect to Stack
  Overflow “HTTP persistent”?

Unless your browser (or a peculiar server) says otherwise, yes.

• Does the COMET technology of server push use this mechanism of HTTP
  persistent connection to push data to
  clients?

Kinda (for streaming, at least), but with a lot of whipped cream on top. There are other Comet implementation approaches, such as hidden iframes and AJAX long polling, that may not require persistent connections (which give some firewalls &c the fits anyway;-).