NAME
send, sendto, sendmsg - send a message from a socket

SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>

cc = send(s, msg, len, flags)
int cc, s;
char *msg;
int len, flags;

cc = sendto(s, msg, len, flags, to, tolen)
int cc, s;
char *msg;
int len, flags;
struct sockaddr *to;
int tolen;

cc = sendmsg(s, msg, flags)
int cc, s;
struct msghdr *msg;
int flags;

DESCRIPTION
Send, sendto, and sendmsg are used to transmit a message to another
socket. Send may be used only when the socket is in a connected
state, while sendto and sendmsg may be used at any time.

The address of the target is given by to with tolen specifying its
size. The length of the message is given by len. If the message
is too long to pass atomically through the underlying protocol,
then the error EMSGSIZE is returned, and the message is not
transmitted.

No indication of failure to deliver is implicit in a send. Return
values of -1 indicate some locally detected errors.

If no messages space is available at the socket to hold the message
to be transmitted, then send normally blocks, unless the socket has
been placed in non-blocking I/O mode. The select(2) call may be
used to determine when it is possible to send more data.

The flags parameter may include one or more of the following:

#define MSG_OOB 0x1 /* process out-of-band data */
#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */

The flag MSG_OOB is used to send "out-of-band" data on sockets that
support this notion (e.g. SOCK_STREAM); the underlying protocol
must also support "out-of-band" data. MSG_DONTROUTE is usually
used only by diagnostic or routing programs.

See recv(2) for a description of the msghdr structure.

RETURN VALUE
The call returns the number of characters sent, or -1 if an error
occurred.

ERRORS
[EBADF] An invalid descriptor was specified.

[ENOTSOCK] The argument s is not a socket.

[EFAULT] An invalid user space address was specified for
a parameter.

[EMSGSIZE] The socket requires that message be sent
atomically, and the size of the message to be
sent made this impossible.

[EWOULDBLOCK] The socket is marked non-blocking and the
requested operation would block.

[ENOBUFS] The system was unable to allocate an internal
buffer. The operation may succeed when buffers
become available.

[ENOBUFS] The output queue for a network interface was
full. This generally indicates that the
interface has stopped sending, but may be
caused by transient congestion.

SEE ALSO
fcntl(2), recv(2), select(2), getsockopt(2), socket(2), write(2)