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Microsoft EPMAP
Microsoft Endpoint Mapper (EPMAP), commonly operating on port 135, serves as the RPC (Remote Procedure Call) locator service. It allows clients to identify network services available on a Windows host, facilitating communication with components like DHCP, DNS, WINS, and Distributed Component Object Model (DCOM). By mapping UUIDs to network addresses, EPMAP acts as a directory, enabling dynamic discovery of RPC services essential for remote management and inter-process communication in Windows environments..
Port 135 is most widely known for hosting the Microsoft Endpoint Mapper (EPM), or DCE/RPC Locator service. It is a critical component of the Microsoft RPC architecture. This service maps UUIDs requested by a client to the network endpoints, allowing the client to discover where a particular RPC service is listening.
Operating in both TCP and UDP protocols, EPMAP listens on port 135 and is fundamental in enabling various distributed Microsoft services. When a client wishes to communicate with a service like the DHCP server, WINS, or the DNS server, it consults the EPMAP service to resolve the service’s endpoint information dynamically. This capability is essential to the underlying Windows network architecture and is heavily utilized by DCOM communications.
Besides core OS functions, many enterprise Microsoft applications and management tools also rely on port 135 for initial handshakes. After this initial discovery phase, most communications occur on dynamically assigned high-numbered ports negotiated via port 135’s RPC endpoint mapper.