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SSDP / UPnP Discovery
Port 1900 is primarily used by the Simple Service Discovery Protocol (SSDP), which is a part of the Universal Plug and Play (UPnP) suite of protocols. It facilitates the discovery of network devices and services on local networks without the need for manual configuration, enabling seamless interoperability among diverse devices such as printers, smart TVs, media servers, and IoT devices..
The Simple Service Discovery Protocol (SSDP) operates over UDP port 1900 to enable automatic discovery of UPnP devices within a local network. Devices broadcast NOTIFY messages and respond to M-SEARCH requests to advertise or discover services. SSDP uses a multicast address (239.255.255.250) to efficiently reach multiple devices simultaneously.
This discovery mechanism allows consumer devices to announce capabilities dynamically, such as media streaming features or printer availability, without user intervention. Control points, such as smartphones or computers, can then browse these devices and interact with their services using standardized protocols.
Despite facilitating plug-and-play ease on home and small office networks, SSDP is limited by its lack of authentication and plaintext communications, making it susceptible to various network abuses. Its reliance on multicast traffic also means excessive or misconfigured devices can generate substantial broadcast traffic, affecting network performance.