LAN Messenger? You mean a Instant Message client? or you talking LAN ADMIN notifications (i.e. Network shut down at 5PM, please log out by 4pm, thank you). Normally you would use your GROUPWARE tools that come with your applications, like for Microsoft Sharepoint uses Lync, or maybe you might use Skype (which is now owned by Microsoft). LAN Messengers were BLOCKED waaaaaayyyyy back 10 years ago in XP because it was a security breach potential, one could push through the LAN Messenger (which did happen) mass spamming 'pop ups', and thus was cut off since.