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Microsoft Notification Protocol
Port 1863 is primarily used by the Microsoft Notification Protocol (MSNP), which underpins the connectivity for Microsoft’s instant messaging clients such as MSN Messenger and legacy .NET Messenger services. This protocol facilitates presence information, instant messaging, and notification delivery to users on these platforms..
The Microsoft Notification Protocol (MSNP) is a proprietary protocol developed by Microsoft to enable communication between Messenger clients and Microsoft's servers. It manages user authentication, presence status updates, message exchange, and notifications related to contacts, such as online/offline status changes. Initially designed for MSN Messenger, MSNP underwent multiple iterations (MSNP2 through MSNP21) featuring enhancements in security and performance.
MSNP operates predominantly over TCP port 1863, initiating and maintaining persistent connections to facilitate real-time message delivery. It uses a text-based command syntax similar to HTTP for command and response exchanges, easing parsing and development. Payloads for messages and notifications are encapsulated within these commands, enabling flexible and extensible communication.
Over time, this protocol was supplemented or replaced by more modern solutions integrated into Microsoft’s messaging infrastructure, transitioning eventually to Skype and Microsoft Teams, which leverage different services. However, remnants of MSNP usage might still be found in legacy systems or deprecated services relying on compatibility layers.