int accept(int socket, struct sockaddr *restrictaddress,
socklen_t *restrictaddress_len);
DESCRIPTION
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
Points to a socklen_t structure 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.
RETURN VALUE
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.
ERRORS
The accept() function shall fail if:
EAGAIN] or [EWOULDBLOCK
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.
ECONNABORTED
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
{OPEN_MAX} file descriptors are currently open in the calling process.
ENFILE
The maximum number of file descriptors in the system are already open.
ENOTSOCK
The socket argument does not refer to a socket.
EOPNOTSUPP
The socket type of the specified socket does not support accepting
connections.
The accept() function may fail if:
ENOBUFS
No buffer space is available.
ENOMEM
There was insufficient memory available to complete the operation.
EPROTO
A protocol error has occurred; for example, the STREAMS protocol stack
has not been initialized.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
When a connection is available, select() indicates that the
file descriptor for
the socket is ready for reading.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
bind() , connect() , listen()
, socket() , the Base Definitions volume of IEEE Std 1003.1-2001,
<sys/socket.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
