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NAME

       send - send a message on a socket

SYNOPSIS

       #include <sys/socket.h>

       ssize_t send(int socket, const void *buffer, size_t length, int flags);

DESCRIPTION

       The  send()  function shall initiate transmission of a message from the specified socket to its peer. The
       send() function shall send a message only when the socket is connected (including  when  the  peer  of  a
       connectionless socket has been set via connect()).

       The send() function takes the following arguments:

       socket Specifies the socket file descriptor.

       buffer Points to the buffer containing the message to send.

       length Specifies the length of the message in bytes.

       flags  Specifies the type of message transmission. Values of this argument are formed by logically OR'ing
              zero or more of the following flags:

       MSG_EOR
              Terminates a record (if supported by the protocol).

       MSG_OOB
              Sends out-of-band data on sockets that support out-of-band communications.  The  significance  and
              semantics of out-of-band data are protocol-specific.

       The  length  of the message to be sent is specified by the length argument. If the message is too long to
       pass through the underlying protocol, send() shall fail and no data shall be transmitted.

       Successful completion of a call to send() does not guarantee delivery of the message. A return  value  of
       -1 indicates only locally-detected errors.

       If  space  is  not  available at the sending socket to hold the message to be transmitted, and the socket
       file descriptor does not have O_NONBLOCK set, send() shall block until space is available.  If  space  is
       not available at the sending socket to hold the message to be transmitted, and the socket file descriptor
       does have O_NONBLOCK set, send() shall fail. The select() and poll() functions can be used  to  determine
       when it is possible to send more data.

       The socket in use may require the process to have appropriate privileges to use the send() function.

RETURN VALUE

       Upon successful completion, send() shall return the number of bytes sent. Otherwise, -1 shall be returned
       and errno set to indicate the error.

ERRORS

       The send() function shall fail if:

       EAGAIN or EWOULDBLOCK

              The socket's file descriptor is marked O_NONBLOCK and the requested operation would block.

       EBADF  The socket argument is not a valid file descriptor.

       ECONNRESET
              A connection was forcibly closed by a peer.

       EDESTADDRREQ

              The socket is not connection-mode and no peer address is set.

       EINTR  A signal interrupted send() before any data was transmitted.

       EMSGSIZE
              The message is too large to be sent all at once, as the socket requires.

       ENOTCONN
              The socket is not connected or otherwise has not had the peer pre-specified.

       ENOTSOCK
              The socket argument does not refer to a socket.

       EOPNOTSUPP
              The socket argument is associated with a socket that does not support one or more  of  the  values
              set in flags.

       EPIPE  The  socket is shut down for writing, or the socket is connection-mode and is no longer connected.
              In the latter case, and if the socket is of type SOCK_STREAM, the SIGPIPE signal is  generated  to
              the calling thread.

       The send() function may fail if:

       EACCES The calling process does not have the appropriate privileges.

       EIO    An I/O error occurred while reading from or writing to the file system.

       ENETDOWN
              The local network interface used to reach the destination is down.

       ENETUNREACH

              No route to the network is present.

       ENOBUFS
              Insufficient resources were available in the system to perform the operation.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       The send() function is equivalent to sendto() with a null pointer dest_len argument, and to write() if no
       flags are used.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       connect() , getsockopt() , poll() , recv() , recvfrom() , recvmsg() , select() , sendmsg() ,  sendto()  ,
       setsockopt()   ,   shutdown()   ,  socket()  ,  the  Base  Definitions  volume  of  IEEE Std 1003.1-2001,
       <sys/socket.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .