Which service uses port 135 TCP/UDP?

• A. Hypertext Transfer Protocol (HTTP)
• B. Microsoft EPMAP
• C. Kerberos—authentication system
• D. Network News Transfer Protocol (NNTP)

Answer: (B)

Port 135 is the RPC Endpoint Mapper used by Windows to locate dynamic RPC service ports. The service that uses this port is Microsoft EPMAP. It listens on 135/TCP and 135/UDP, and its role is to tell a client which high-numbered port to connect to for a given RPC service. When a client needs to invoke a remote RPC service, it first contacts the endpoint mapper on port 135 to learn the actual port where that service is listening, then switches to that port for the conversation. Other options operate on different standard ports: HTTP uses 80, Kerberos uses 88, and NNTP uses 119.