WinNT Messenger service & Winpop

WinNT Messenger service and Winpopup uses mailslot to comunicate on network, but I couldn’t find any info covering format of msg they send. I suppose it should be smth like that: “Recipient”+#0+”Sender”+#0+”msg text”, but maybe I’m wrong. And 1 morething – how to write to mailslot using some specific protocol, not all available on PC.
Thanx!
Normunds