Returns a list describing all existing listening points, including the default one set up automatically by the server when it was started (unless that one has since been destroyed by a call to `unlisten()'). Each element of the list has the following form:
{<object>, <canon>, <print-messages>}
where <object> is the first argument given in the call to `listen()' to create this listening point, <print-messages> is true if the third argument in that call was provided and true, and <canon> was the value returned by that call. (For the initial listening point, <object> is #0, <canon> is determined by the command-line arguments or a network-configuration-specific default, and <print-messages> is true.)