ACCEPT(3)                  POSIX Programmer's Manual                 ACCEPT(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
       accept -- accept a new connection on a socket

SSYYNNOOPPSSIISS
       #include <sys/socket.h>

       int accept(int _s_o_c_k_e_t, struct sockaddr *restrict _a_d_d_r_e_s_s,
           socklen_t *restrict _a_d_d_r_e_s_s___l_e_n);

DDEESSCCRRIIPPTTIIOONN
       The _a_c_c_e_p_t() function shall extract the first connection on the queue
       of pending connections, create a new socket with the same socket type
       protocol and address family as the specified socket, and allocate a new
       file descriptor for that socket. The file descriptor shall be allocated
       as described in _S_e_c_t_i_o_n _2_._1_4, _F_i_l_e _D_e_s_c_r_i_p_t_o_r _A_l_l_o_c_a_t_i_o_n.

       The _a_c_c_e_p_t() function takes the following arguments:

       _s_o_c_k_e_t      Specifies a socket that was created with _s_o_c_k_e_t(), has been
                   bound to an address with _b_i_n_d(), and has issued a
                   successful call to _l_i_s_t_e_n().

       _a_d_d_r_e_s_s     Either a null pointer, or a pointer to a ssoocckkaaddddrr structure
                   where the address of the connecting socket shall be
                   returned.

       _a_d_d_r_e_s_s___l_e_n Either a null pointer, if _a_d_d_r_e_s_s is a null pointer, or a
                   pointer to a ssoocckklleenn__tt object which on input specifies the
                   length of the supplied ssoocckkaaddddrr structure, and on output
                   specifies the length of the stored address.

       If _a_d_d_r_e_s_s is not a null pointer, the address of the peer for the
       accepted connection shall be stored in the ssoocckkaaddddrr structure pointed
       to by _a_d_d_r_e_s_s, and the length of this address shall be stored in the
       object pointed to by _a_d_d_r_e_s_s___l_e_n.

       If the actual length of the address is greater than the length of the
       supplied ssoocckkaaddddrr structure, the stored address shall be truncated.

       If the protocol permits connections by unbound clients, and the peer is
       not bound, then the value stored in the object pointed to by _a_d_d_r_e_s_s is
       unspecified.

       If the listen queue is empty of connection requests and O_NONBLOCK is
       not set on the file descriptor for the socket, _a_c_c_e_p_t() shall block
       until a connection is present. If the _l_i_s_t_e_n() queue is empty of
       connection requests and O_NONBLOCK is set on the file descriptor for
       the socket, _a_c_c_e_p_t() shall fail and set _e_r_r_n_o to [[EEAAGGAAIINN]] or
       [[EEWWOOUULLDDBBLLOOCCKK]].

       The accepted socket cannot itself accept more connections. The original
       socket remains open and can accept more connections.

RREETTUURRNN VVAALLUUEE
       Upon successful completion, _a_c_c_e_p_t() shall return the non-negative file
       descriptor of the accepted socket.  Otherwise, -1 shall be returned,
       _e_r_r_n_o shall be set to indicate the error, and any object pointed to by
       _a_d_d_r_e_s_s___l_e_n shall remain unchanged.

EERRRROORRSS
       The _a_c_c_e_p_t() function shall fail if:

       EEAAGGAAIINN or EEWWOOUULLDDBBLLOOCCKK
              O_NONBLOCK is set for the socket file descriptor and no
              connections are present to be accepted.

       EEBBAADDFF  The _s_o_c_k_e_t argument is not a valid file descriptor.

       EECCOONNNNAABBOORRTTEEDD
              A connection has been aborted.

       EEIINNTTRR  The _a_c_c_e_p_t() function was interrupted by a signal that was
              caught before a valid connection arrived.

       EEIINNVVAALL The _s_o_c_k_e_t is not accepting connections.

       EEMMFFIILLEE All file descriptors available to the process are currently
              open.

       EENNFFIILLEE The maximum number of file descriptors in the system are already
              open.

       EENNOOBBUUFFSS
              No buffer space is available.

       EENNOOMMEEMM There was insufficient memory available to complete the
              operation.

       EENNOOTTSSOOCCKK
              The _s_o_c_k_e_t argument does not refer to a socket.

       EEOOPPNNOOTTSSUUPPPP
              The socket type of the specified socket does not support
              accepting connections.

       The _a_c_c_e_p_t() function may fail if:

       EEPPRROOTTOO A protocol error has occurred; for example, the STREAMS protocol
              stack has not been initialized.

       _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
       When a connection is available, _s_e_l_e_c_t() indicates that the file
       descriptor for the socket is ready for reading.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _S_e_c_t_i_o_n _2_._1_4, _F_i_l_e _D_e_s_c_r_i_p_t_o_r _A_l_l_o_c_a_t_i_o_n, _b_i_n_d(), _c_o_n_n_e_c_t(), _l_i_s_t_e_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                            ACCEPT(3)
