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



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

NNAAMMEE
       send -- send a message on a socket

SSYYNNOOPPSSIISS
       #include <sys/socket.h>

       ssize_t send(int _s_o_c_k_e_t, const void *_b_u_f_f_e_r, size_t _l_e_n_g_t_h, int _f_l_a_g_s);

DDEESSCCRRIIPPTTIIOONN
       The _s_e_n_d() function shall initiate transmission of a message from the
       specified socket to its peer. The _s_e_n_d() 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 _s_e_n_d() function takes the following arguments:

       _s_o_c_k_e_t      Specifies the socket file descriptor.

       _b_u_f_f_e_r      Points to the buffer containing the message to send.

       _l_e_n_g_t_h      Specifies the length of the message in bytes.

       _f_l_a_g_s       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
                                 [[EEPPIIPPEE]] error shall still be returned.

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

       Successful completion of a call to _s_e_n_d() 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, _s_e_n_d() 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, _s_e_n_d() shall
       fail. The _s_e_l_e_c_t() and _p_o_l_l() 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 _s_e_n_d() function.

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

EERRRROORRSS
       The _s_e_n_d() function shall fail if:

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

       EEBBAADDFF  The _s_o_c_k_e_t argument is not a valid file descriptor.

       EECCOONNNNRREESSEETT
              A connection was forcibly closed by a peer.

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

       EEIINNTTRR  A signal interrupted _s_e_n_d() before any data was transmitted.

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

       EENNOOTTCCOONNNN
              The socket is not connected.

       EENNOOTTSSOOCCKK
              The _s_o_c_k_e_t argument does not refer to a socket.

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

       EEPPIIPPEE  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 _s_e_n_d() function may fail if:

       EEAACCCCEESS The calling process does not have appropriate privileges.

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

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

       EENNEETTUUNNRREEAACCHH
              No route to the network is present.

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

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       If the _s_o_c_k_e_t argument refers to a connection-mode socket, the _s_e_n_d()
       function is equivalent to _s_e_n_d_t_o() (with any value for the _d_e_s_t___a_d_d_r
       and _d_e_s_t___l_e_n arguments, as they are ignored in this case). If the
       _s_o_c_k_e_t argument refers to a socket and the _f_l_a_g_s argument is 0, the
       _s_e_n_d() function is equivalent to _w_r_i_t_e().

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _c_o_n_n_e_c_t(), _g_e_t_s_o_c_k_o_p_t(), _p_o_l_l(), _p_s_e_l_e_c_t(), _r_e_c_v(), _r_e_c_v_f_r_o_m(),
       _r_e_c_v_m_s_g(), _s_e_n_d_m_s_g(), _s_e_n_d_t_o(), _s_e_t_s_o_c_k_o_p_t(), _s_h_u_t_d_o_w_n(), _s_o_c_k_e_t(),
       _w_r_i_t_e()

       The Base Definitions volume of POSIX.1-2017, <<ssyyss__ssoocckkeett..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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                  2017                              SEND(3)
