Mailslot

Mailslot is a one-way interprocess communication mechanism, available on the Microsoft Windows operating system that allows communication between processes locally. Mailslots also supported communication over a network. The use of Mailslots is generally simpler than named pipes or sockets when a relatively small number of relatively short messages is expected to be transmitted, such as for example infrequent state-change messages, or as part of a peer-discovery protocol. Up until Windows 11 24H2, the Mailslot mechanism also allowed for short message broadcasts ("datagrams") to all listening computers across a given network domain. The mechanism originated in LAN Manager, a component of OS/2, an operating system co-developed by IBM and Microsoft. Mailslots were discontinued in Windows 11 24H2.

Mailslot is a one-way interprocess communication mechanism, available on the Microsoft Windows operating system that allows communication between processes locally. Mailslots also supported communication over a network. The use of Mailslots is generally simpler than named pipes or sockets when a relatively small number of relatively short messages is expected to be transmitted, such as for example infrequent state-change messages, or as part of a peer-discovery protocol. Up until Windows 11 24H2, the Mailslot mechanism also allowed for short message broadcasts ("datagrams") to all listening computers across a given network domain. The mechanism originated in LAN Manager, a component of OS/2, an operating system co-developed by IBM and Microsoft. Mailslots were discontinued in Windows 11 24H2. ==Features== Mailslots function as a server-client interface. A server can create a Mailslot, and a client could write to it by name. Only the server can read the mailslot, as such mailslots represented a one-way communication mechanism. A server-client interface could consist of two processes communicating locally or across a network. Mailslots operated over the RPC protocol and worked across all computers in the same network domain. Mailslots offered no confirmation that a message had been received. Mailslots were generally a good choice when one client process need to broadcast a message to multiple server processes. ==Uses== The most widely known use of the Mailslot IPC mechanism was the Windows Messenger service that was part of the Windows NT-line of products, including Windows XP. The Messenger Service, not to be confused with the MSN Messenger internet chat service, was essentially a Mailslot server that waited for a message to arrive. When a message arrived, it was displayed in a popup onscreen. The NET SEND command was therefore a type of Mailslot client, because it wrote to specified mailslots on a network. A number of programs also used Mailslots to communicate. Generally these were amateur chat clients and other such programs . Commercial programs usually preferred pipes or sockets. Mailslots were implemented as files in a mailslot file system (MSFS). Examples of Mailslots included: MAILSLOT\Messngr - Microsoft NET SEND Protocol MAILSLOT\Browse - Microsoft Browser Protocol MAILSLOT\Alerter MAILSLOT\53cb31a0\UnimodemNotifyTSP MAILSLOT\HydraLsServer - Microsoft Terminal Services Licensing MAILSLOT\CheyenneDS - CA BrightStor Discovery Service ==References== ==External links== Mailslots (MSDN Documentation) Using Mailslots for Interprocess Communication Using a Mailslot to read/write data over a network The beginning of the end of Remote Mailslots

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