PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SEND(3P)                  POSIX Programmer's Manual                 SEND(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       send — send a message on a socket

SYNOPSIS         top

       #include <sys/socket.h>

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

DESCRIPTION         top

       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. If the socket is a
       connectionless-mode socket, the message shall be sent to the pre-
       specified peer address.

       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.

                   MSG_NOSIGNAL  Requests not to send the SIGPIPE signal if
                                 an attempt to send is made on a stream-
                                 oriented socket that is no longer
                                 connected. The [EPIPE] error shall still be
                                 returned.

       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         top

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

ERRORS         top

       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.

       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 or
              SOCK_SEQPACKET and the MSG_NOSIGNAL flag is not set, the
              SIGPIPE signal is generated to the calling thread.

       The send() function may fail if:

       EACCES The calling process does not have 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         top

       None.

APPLICATION USAGE         top

       If the socket argument refers to a connection-mode socket, the send()
       function is equivalent to sendto() (with any value for the dest_addr
       and dest_len arguments, as they are ignored in this case). If the
       socket argument refers to a socket and the flags argument is 0, the
       send() function is equivalent to write().

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       connect(3p), getsockopt(3p), poll(3p), pselect(3p), recv(3p),
       recvfrom(3p), recvmsg(3p), sendmsg(3p), sendto(3p), setsockopt(3p),
       shutdown(3p), socket(3p), write(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_socket.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                            SEND(3P)