SENDTO(3)                  POSIX Programmer's Manual                 SENDTO(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
       sendto -- send a message on a socket

SSYYNNOOPPSSIISS
       #include <sys/socket.h>

       ssize_t sendto(int _s_o_c_k_e_t, const void *_m_e_s_s_a_g_e, size_t _l_e_n_g_t_h,
           int _f_l_a_g_s, const struct sockaddr *_d_e_s_t___a_d_d_r,
           socklen_t _d_e_s_t___l_e_n);

DDEESSCCRRIIPPTTIIOONN
       The _s_e_n_d_t_o() function shall send a message through a connection-mode or
       connectionless-mode socket.

       If the socket is a connectionless-mode socket, the message shall be
       sent to the address specified by _d_e_s_t___a_d_d_r if no pre-specified peer
       address has been set. If a peer address has been pre-specified, either
       the message shall be sent to the address specified by _d_e_s_t___a_d_d_r
       (overriding the pre-specified peer address), or the function shall
       return -1 and set _e_r_r_n_o to [[EEIISSCCOONNNN]].

       If the socket is connection-mode, _d_e_s_t___a_d_d_r shall be ignored.

       The _s_e_n_d_t_o() function takes the following arguments:

       _s_o_c_k_e_t      Specifies the socket file descriptor.

       _m_e_s_s_a_g_e     Points to a buffer containing the message to be sent.

       _l_e_n_g_t_h      Specifies the size 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 data. 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.

       _d_e_s_t___a_d_d_r   Points to a ssoocckkaaddddrr structure containing the destination
                   address. The length and format of the address depend on the
                   address family of the socket.

       _d_e_s_t___l_e_n    Specifies the length of the ssoocckkaaddddrr structure pointed to
                   by the _d_e_s_t___a_d_d_r argument.

       If the socket protocol supports broadcast and the specified address is
       a broadcast address for the socket protocol, _s_e_n_d_t_o() shall fail if the
       SO_BROADCAST option is not set for the socket.

       The _d_e_s_t___a_d_d_r argument specifies the address of the target.

       The _l_e_n_g_t_h argument specifies the length of the message.

       Successful completion of a call to _s_e_n_d_t_o() 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_t_o() 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_t_o() shall
       fail.

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

RREETTUURRNN VVAALLUUEE
       Upon successful completion, _s_e_n_d_t_o() 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_t_o() function shall fail if:

       EEAAFFNNOOSSUUPPPPOORRTT
              Addresses in the specified address family cannot be used with
              this socket.

       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.

       EEIINNTTRR  A signal interrupted _s_e_n_d_t_o() 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 connection-mode but 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.

       If the address family of the socket is AF_UNIX, then _s_e_n_d_t_o() shall
       fail if:

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

       EELLOOOOPP  A loop exists in symbolic links encountered during resolution of
              the pathname in the socket address.

       EENNAAMMEETTOOOOLLOONNGG
              The length of a component of a pathname is longer than
              {NAME_MAX}.

       EENNOOEENNTT A component of the pathname does not name an existing file or
              the pathname is an empty string.

       EENNOOTTDDIIRR
              A component of the path prefix of the pathname in the socket
              address names an existing file that is neither a directory nor a
              symbolic link to a directory, or the pathname in the socket
              address contains at least one non-<slash> character and ends
              with one or more trailing <slash> characters and the last
              pathname component names an existing file that is neither a
              directory nor a symbolic link to a directory.

       The _s_e_n_d_t_o() function may fail if:

       EEAACCCCEESS Search permission is denied for a component of the path prefix;
              or write access to the named socket is denied.

       EEDDEESSTTAADDDDRRRREEQQ
              The socket is not connection-mode and does not have its peer
              address set, and no destination address was specified.

       EEHHOOSSTTUUNNRREEAACCHH
              The destination host cannot be reached (probably because the
              host is down or a remote router cannot reach it).

       EEIINNVVAALL The _d_e_s_t___l_e_n argument is not a valid length for the address
              family.

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

       EEIISSCCOONNNN
              A destination address was specified and the socket is already
              connected.

       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.

       EENNOOMMEEMM Insufficient memory was available to fulfill the request.

       If the address family of the socket is AF_UNIX, then _s_e_n_d_t_o() may fail
       if:

       EELLOOOOPP  More than {SYMLOOP_MAX} symbolic links were encountered during
              resolution of the pathname in the socket address.

       EENNAAMMEETTOOOOLLOONNGG
              The length of a pathname exceeds {PATH_MAX}, or pathname
              resolution of a symbolic link produced an intermediate result
              with a length that exceeds {PATH_MAX}.

       _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
       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.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _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(),
       _s_e_n_d_m_s_g(), _s_e_t_s_o_c_k_o_p_t(), _s_h_u_t_d_o_w_n(), _s_o_c_k_e_t()

       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                            SENDTO(3)
