The svc_getreqset routine is for servers that implement custom
    asynchronous event processing or that do not use the svc_run
    routine. You can only use svc_fdset when the server does not use
    svc_run.

    You are unlikely to call this routine directly, because the
    svc_run routine calls it. However, there are times when you
    cannot call svc_run. For example, suppose a program services
    RPC requests and reads or writes to another socket at the same
    time. The program cannot call svc_run. It must call select and
    svc_getreqset.

    The server calls svc_getreqset when a call to the select system
    call determines that the server has received one or more RPC
    requests. The svc_getreqset routine reads in data for each server
    connection, then calls the server program to handle the data.

    The svc_getreqset routine does not return a value. It finishes
    executing after all sockets associated with the variable rdfds
    have been serviced.

    You can use the global variable svc_fdset with svc_getreqset. The
    svc_fdset variable is the RPC server's read file descriptor bit
    mask.

    To use svc_fdset:
    1. Copy the global variable svc_fdset into a temporary variable.
    2. Pass the temporary variable to the select routine. The select
       routine overwrites the variable and returns it.
    3. Pass the temporary variable to the svc_getreqset routine.