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NAME
accept - accept a connection on a socket
SYNOPSIS
#include <network.h>
int accept(int s, struct sockaddr *addr, int *addrlen);
DESCRIPTION
The argument s is a socket that has been created with
socket(2), bound to an address with bind(2), and is lis-
tening for connections after a listen(2). The accept
function extracts the first connection request on the
queue of pending connections, creates a new socket with
the same properties of s, and allocates a new file
descriptor for the socket. If no pending connections are
present on the queue, and the socket is not marked as non-
blocking, accept blocks the caller until a connection is
present. If the socket is marked non-blocking and no
pending connections are present on the queue, accept
returns an error as described below. The socket returned
by accept may not be used to accept more connections. The
original socket s remains open.
The argument addr is a result parameter that is filled in
with the address of the connecting entity, as known to the
communications layer. The exact format of the addr param-
eter is determined by the domain in which the communica-
tion is occurring. addrlen is a value-result parameter:
it should initially contain the amount of space pointed to
by addr; on return it will contain the actual length (in
bytes) of the address returned. This call is used with
connection-based socket types, currently with SOCK_STREAM.
It is possible to select(2) a socket for the purposes of
doing an accept by selecting it for read.
For certain protocols which require an explicit confirma-
tion, such as DECNet, accept can be thought of as merely
dequeuing the next connection request and not implying
confirmation. Confirmation can be implied by a normal
read or write on the new file descriptor, and rejection
can be implied by closing the new socket. Currently only
DECNet has these semantics on Linux.
NOTES
If you want accept to never block the listening socket
needs to have the non blocking flag set. Assuming that
there is always a connection waiting after select returned
true is not reliable, because the connection might be
removed by an asynchronous network error between the
select/poll returning and the accept call. The application
would hang then if the listen socket is not non blocking.
RETURN VALUES
The call returns -1 on error. If it succeeds, it returns
a non-negative integer that is a descriptor for the
accepted socket.
ERRORS
EBADF The descriptor is invalid.
ENOTSOCK
The descriptor references a file, not a socket.
EOPNOTSUPP
The referenced socket is not of type SOCK_STREAM.
EAGAIN The socket is marked non-blocking and no connec-
tions are present to be accepted.
ENOBUFS, ENOMEM
Not enough free memory.
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