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

 s
    A socket descriptor created with the socket() function.
 msg
 flags
    A bit mask that can contain one or more of the following
    flags. The mask is built by using a logical OR operation on the
    appropriate values.
    Flag               Description
    MSG_OOB            Allows you to receive out-of-band data.
                       If out-of-band data is available, it is read
                       first. If no out-of-band data is available,
                       the MSG_OOB flag is ignored. Use send(),
                       sendmsg(), and sendto()  functions to send
                       out-of-band data.
    MSG_PEEK           Allows you to peek at the data that is next in
                       line to be received without actually removing
                       it from the system's buffers.