SEND(2)                              BSD                               SEND(2)



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 can be used only when the socket is in a connected state,
     while sendto and sendmsg can 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 can 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 (for example, 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.

ERRORS
     These calls will fail if any of the following are true:

     [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)

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