I have activated the Apache server status module on my Apache server. But I do not understand all the informations on the page. I which to know if number of requests means number of machines connected to my server. I can read this :
2 requests currently being processed, 62 idle workers
Total accesses: 32869 - Total Traffic: 111.8 MB
.123 requests/sec - 438 B/second - 3553 B/request
Server load: -1.00 -1.00 -1.00
What does all that means
In your example, the 2 requests currently being processed is how many machines are connected to your server at that moment. Idle workers is Apache processes waiting for a connection to come in. Total accesses is the number of accesses since the last time Apache was restarted.
I would say that you cannot get an exact number of machines, but as said by @sa289, number of requests being processed will give you an approximation. Reason why this cannot be considered an exact data is because most browsers make concurrent connections for one "visit", say for instance, one for downloading the "main" html file, one downloading the css stylesheet, one downloading the js script, etc.
http://kb.mozillazine.org/Network.http.max-connections-per-server https://support.microsoft.com/en-us/kb/282402