Wait, now I'm lost. You keep saying the
browser is sending you things. So you're the
webserver in this scenario? In that case the HTTP 1.1 stuff is irrelevant.
There are two ways to detect the end of the data being sent by the client depending on the type of request they're making. If it's a GET/HEAD request then you just read until you hit two consecutive CRLF's marking the end of the headers (there can't be any data) and if it's a POST there should always be a Content-Length header telling you the amount of data being sent.
If you're using sockets and HTTP you should really
read up on the HTTP protocol, especially if you're writing some kind of web server.