steam_is_user_logged_on

This function will return true if the Steam client currently has a live connection to the Steam servers. If it returns false, it means there is no active connection due to either a networking issue on the local machine, or the Steam server being down or busy.

Syntax:

steam_is_user_logged_on();

Returns:

String

Example:

if steam_is_user_logged_on()
    {
    global.user_id = steam_get_user_account_id();
    }

The above code will check to see if the user is logged onto the Steam server and if it stores the user ID in a global variable.