VMS Help TCPIP Services, Programming Interfaces, Sockets API, recvmsg(), Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    You can use this function with any socket, whether or not it
    is in a connected state. It receives data sent by a call to
    sendmsg(), send(),  or sendto(). The message is scattered into
    several user buffers if such buffers are specified.
    To receive data, the socket does not need to be connected to
    another socket.
    When the ioveciovcnt array specifies more than one buffer, the
    input data is scattered into iovcnt buffers as specified by the
    members of the iovec array:
    iov0, iov1, ..., ioviovcnt
    When a message is received, it is split among the buffers by
    filling the first buffer in the list, then the second, and so on,
    until either all of the buffers are full or there is no more data
    to be placed in the buffers.
    You can use the select() function to determine when more data
    arrives.
    Related Functions
    See also read(), send(),  and socket().