4.5 Connectionless Client Communicating with a Dynamic Server Endpoint

The following example illustrates a connectionless client issuing a sequence of calls to a server that uses a dynamic UDP endpoint.

Connectionless client issuing a sequence of calls

Figure 26: Connectionless client issuing a sequence of calls

Initially, the client has no knowledge of the server's actual endpoint, so the first request PDU (packet #1) is sent to the endpoint mapper port for UDP, which is port 135.

The endpoint mapper forwards the request and the client endpoint to the RPC server in an implementation-dependent way (packet #2).

The server processes the request, as usual, and replies directly to the client endpoint (packet #3).

While processing the received PDU, the client updates its internal structures (Client Address Space, Server's endpoint) so that further PDUs belonging to this activity are sent directly to the correct server port. After this point, the client communicates directly with the RPC server (request #4 and reply #5).