ACCEPT(2)						      BSD System Calls Manual							 ACCEPT(2)

NAME

     accept -- accept a connection on a socket

SYNOPSIS

     #include <sys/types.h>
     #include <sys/socket.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 listening for connections after a
     listen(2).  The accept() argument 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 accepted socket may not be used to accept more con-
     nections.	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 parameter is determined by the domain in which the communication is occurring.  The 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 confirmation, such as ISO or DATAKIT, 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.

     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).

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

     The accept() will fail if:

     [EBADF]		The descriptor is invalid.

     [ENOTSOCK] 	The descriptor references a file, not a socket.

     [EOPNOTSUPP]	The referenced socket is not of type SOCK_STREAM.

     [EFAULT]		The addr parameter is not in a writable part of the user address space.

     [EWOULDBLOCK]	The socket is marked non-blocking and no connections are present to be accepted.

     [EMFILE]		The per-process descriptor table is full.

     [ENFILE]		The system file table is full.

SEE ALSO

     bind(2), connect(2), listen(2), select(2), socket(2)

HISTORY

     The accept() function appeared in 4.2BSD.

4.2 Berkeley Distribution					 December 11, 1993					 4.2 Berkeley Distribution