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       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 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 unspecified.

       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 and errno set to indicate the error.


       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 open.

              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 connections.

       The accept() function may fail if:

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

       The following sections are informative.




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






       bind(), connect(), listen(), socket()

       The Base Definitions volume of POSIX.1‐2008, <sys_socket.h>


       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 .

       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 .