OSF DCE Application Development Guide--Core Components

Topics in RPC Application Development
How the runtime handles a given request depends partly on the communications protocol
over which it arrives, as follows:
• A call over a connectionless transport is routed by the server’s system to the call
request buffer for the endpoint specified in the call.
• A call over a connection-oriented transport may be routed by the server’s system to a
request buffer or the call may go directly to the server process.
Whether a remote procedure call goes to the request buffer depends on whether the
client sends the call over an established connection. If a client makes a remote
procedure call without an established connection, the server’s system treats the call
request as a connection request and places the call request into a request buffer. If an
established connection is available, the client uses it for the remote procedure call;
the system handles the call as an incoming call and sends it directly to the server
process that owns the connection.
Whether a server gets an incoming call from a request buffer or over an existing
connection, the server process manages the call identically. A server process applies a
clear set of call-routing criteria to decide whether to dispatch a call immediately, queue
it, or reject it (if the server is extremely busy). These call-routing criteria are discussed
in Section 16.6.3.
When telling the RPC runtime to use a protocol sequence, a server specifies the number
of calls it can buffer for the specified communications protocol (at a given endpoint).
Usually, it is best for a server to specify a default buffer size, represented by a literal
whose underlying value depends on the communications protocol. The default equals
the capacity of a single socket used for the protocol by the server’s system.
The default usually is adequate to allow the RPC runtime to accept all the incoming call
requests. For a well-known endpoint, the size of a request buffer cannot exceed the
capacity of a single socket descriptor (the default size); specifying a higher number
causes a runtime error. For well-known endpoints, specify the default for the maximum
number of call requests.
For example, consider the request buffer at full capacity as represented in Figure 16-6.
This buffer has the capacity to store five requests. In this example, the buffer is full, and
the runtime rejects incoming requests, as is happening to the sixth request.
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