s
    A socket descriptor created with the socket() function that was
    connected to another socket using the accept() or connect()
    function.
 msg
    A pointer to a buffer containing the data to be sent.
 len
    The length, in bytes, of the data pointed to by msg.
 flags
    Can be either 0 or MSG_OOB. If it is MSG_OOB, the data is sent
    out of band. Data can be received before other pending data on
    the receiving socket if the receiver also specifies MSG_OOB in
    the flag argument of its recv() or recvfrom()  call.