|ACCEPT(2)||System Calls Manual||ACCEPT(2)|
accept — accept a
connection on a socket
struct sockaddr *restrict address,
socklen_t *restrict address_len);
The argument socket is a socket that has
been created with socket(2), bound to
an address with bind(2), and is listening
for connections after a listen(2).
extracts the first connection request on the queue of pending connections,
creates a new socket with the same properties of
socket, 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
accepted socket may not be used to accept more connections. The original
socket socket, remains open.
The argument address 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 address
parameter is determined by the domain in which the communication is
occurring. The address_len is a value-result
parameter; it should initially contain the amount of space pointed to by
address; 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
For certain protocols which require an explicit
confirmation, such as ISO or DATAKIT,
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
One can obtain user connection request data without confirming the connection by issuing a recvmsg(2) call with an msg_iovlen of 0 and a non-zero msg_controllen, or by issuing a getsockopt(2) request. Similarly, one can provide user connection rejection information by issuing a sendmsg(2) call with providing only the control information, or by calling setsockopt(2).
The call returns -1 on error and the global variable errno is set to indicate the error. If it succeeds, it returns a non-negative integer that is a descriptor for the accepted socket.
accept() system call will fail if:
accept() system call was terminated by a signal.
SOCK_STREAMand thus does not accept connections.
The include file
accept() function appeared in
|March 18, 2015||BSD 4.2|