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Zephyr Notification Service
Port 2103 is primarily associated with the Zephyr Notification Service developed under MIT's Project Athena. This service enables real-time messaging and notification delivery across distributed computing environments, allowing users to receive alerts, chat, and status updates..
The Zephyr Notification Service is a distributed instant messaging protocol originally designed as part of MIT's Project Athena. Its key design goal was to support secure, scalable, and real-time delivery of notifications, presence information, and messaging across campus networks, largely predating modern IM systems.
Zephyr operates on a client-server architecture, where the client (both CLI and GUI implementations exist) communicates with the Zephyr servers through well-defined ports—typically including port 2103 (zephyr-clt) for serv-hm connections. This facilitates host-manager interchanges necessary to maintain subscriptions, update presence, and route messages efficiently among users across different systems.
The protocol leverages UDP and TCP for message delivery, enabling both quick, connectionless notification along with more reliable, stateful exchanges. Zephyr uses authentication systems (such as Kerberos) to verify user identity, although plaintext traffic is often transmitted without encryption unless additional security layers are implemented.