send(2)

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

C SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>
     int send(int s, const void *msg, int len, int flags);
     int sendto(int s, const void *msg, int len, int flags,
               struct sockaddr *to, int tolen);
     int sendmsg(int s, const 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 when the socket is unconnected.

     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.

     Usually no indication of failure to deliver is implicit in a send.
     Return values of -1 indicate some locally detected errors.  Connected
     datagram sockets may receive error indications from a previous send.

     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.

     [ECONNREFUSED]      The remote port was invalid when using the send call
                         on a connected datagram socket.

     [EISCONN]           A sendto or sendmsg call was used on a connected
                         socket.

     [EACCES]            The requested operation specified a broadcast address
                         as the destination but the SO_BROADCAST socket option
                         was not enabled (see setsockopt(2)).

     [EHOSTUNREACH]      The remote host was unreachable via the network.

     [ENETUNREACH]       The remote network is unknown to the routing system.

     [EHOSTDOWN]         The remote host was determined to be down, possibly
                         due to a failure to resolve its MAC-level address
                         (see arp(7P)).

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

NOTE
     ABI-compliant versions of the above call can be obtained from
     libsocket.so.