bsd man page for accept

ACCEPT(2)							System Calls Manual							 ACCEPT(2)

NAME
       accept - accept a connection on a socket

SYNOPSIS
       #include <sys/types.h>
       #include <sys/socket.h>

       ns = accept(s, addr, addrlen)
       int ns, 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).  Accept extracts the first connection on the queue of pending connections, creates a new socket with the same  properties  of  s
       and  allocates a new file descriptor, ns, 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, ns, 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 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.

RETURN VALUE
       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.

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

4.2 Berkeley Distribution					   May 22, 1986 							 ACCEPT(2)