Number of visitors online

Ever wondered how sites display the number of visitors currently using the site? It's actually quite simple in ASP. First, add the following code to a global.asa file

<script language="vbscript" runat = "server">
Sub Application_OnStart
    'initialize variable
    Application("visitors_online") = 0
End Sub
Sub Application_OnEnd

End Sub

Sub Session_OnStart
    Session.Timeout = 20 '20 minute timeout
    Application.Lock
    Application("visitors_online") = Application("visitors_online") + 1
    Application.Unlock
End Sub
Sub Session_OnEnd
    Application.Lock
    Application("visitors_online") = Application("visitors_online") - 1
    Application.Unlock
End Sub
</script>

This script is run by IIS. When a session starts, it calls Session_OnStart, and when it ends, it calls Session_OnEnd, allowing you to keep track of the number of active visitors. You can then display the number of visitors online by using

There are currently <%=Application("visitors_online")%> visitor(s) online