MSDN

/*

int send (
SOCKET s,
const char FAR * buf,
int len,
int flags
);

The flags parameter can be used to influence the behavior of the function beyond the options specified for the associated socket. The semantics of this function are determined by the socket options and the flags parameter. The latter is constructed by or-ing the following values:

Value Meaning
MSG_DONTROUTE Specifies that the data should not be subject to routing. A
Windows Sockets service provider can choose to ignore this
flag.

MSG_OOB Send out-of-band data (stream-style socket such as SOCK_STREAM
only. Also see DECnet Out-Of-band data for a discussion of this
topic).

*/