\\[destination]\mailslot\\messngr is a mailslot name used for sending messages on a network. This name is undocumented, though is widely used exactly for this purpose.

In WinNT/Win2K network you can choose any computer or server name on your network as a destination. An asterick (*) is for the primary domain. With this name chosen as a destination the message is delivered to all computers.

It works very similar to NET SEND command.

Christof Lange wrote an article "Send Messages on the Network" published in Nov. 2001 issue of the FoxPro Advisor magazine.

Foxpro sample code (members area):
Using mailslots to send messages on the network
http://www.news2news.com/vfp/?example=269