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

       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.

       accept — accept a new connection on a socket

       #include <sys/socket.h>

       int accept(int socket, struct sockaddr *restrict address,
           socklen_t *restrict address_len);

       The accept() 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 Section 2.14, File Descriptor Allocation.

       The accept() function takes the following arguments:

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

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

       address_len Either a null pointer, if address is a null pointer, or a
                   pointer to a socklen_t object which on input specifies the
                   length of the supplied sockaddr structure, and on output
                   specifies the length of the stored address.

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

       If the actual length of the address is greater than the length of the
       supplied sockaddr 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 address is

       If the listen queue is empty of connection requests and O_NONBLOCK is not
       set on the file descriptor for the socket, accept() shall block until a
       connection is present. If the listen() queue is empty of connection
       requests and O_NONBLOCK is set on the file descriptor for the socket,
       accept() shall fail and set errno to [EAGAIN] or [EWOULDBLOCK].

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

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

       The accept() function shall fail if:

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

       EBADF  The socket argument is not a valid file descriptor.

              A connection has been aborted.

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

       EINVAL The socket is not accepting connections.

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

       ENFILE The maximum number of file descriptors in the system are already

              No buffer space is available.

       ENOMEM There was insufficient memory available to complete the operation.

              The socket argument does not refer to a socket.

              The socket type of the specified socket does not support accepting

       The accept() function may fail if:

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

       The following sections are informative.


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



       Section 2.14, File Descriptor Allocation, bind(), connect(), listen(),

       The Base Definitions volume of POSIX.1‐2017, <sys_socket.h>

       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 .

       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 .

IEEE/The Open Group                   2017                            ACCEPT(3P)