[unix-history] / usr / src / man / man2 / accept.2

.\" Copyright (c) 1983 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)accept.2	6.3 (Berkeley) 5/22/86
.\"
.TH ACCEPT 2 "May 22, 1986"
.UC 5
.SH NAME
accept \- accept a connection on a socket
.SH SYNOPSIS
.ft B
.nf
#include <sys/types.h>
#include <sys/socket.h>
.PP
.ft B
ns = accept(s, addr, addrlen)
int ns, s;
struct sockaddr *addr;
int *addrlen;
.fi
.SH DESCRIPTION
The argument
.I s
is a socket that has been created with
.IR socket (2),
bound to an address with
.IR bind (2),
and is listening for connections after a
.IR listen (2).
.I Accept
extracts the first connection
on the queue of pending connections, creates
a new socket with the same properties of 
.I s
and allocates a new file descriptor,
.IR ns ,
for the socket.  If no pending connections are
present on the queue, and the socket is not marked
as non-blocking,
.I 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, 
.I accept
returns an error as described below.
The accepted socket,
.IR ns ,
may not be used
to accept more connections.  The original socket
.I s
remains open.
.PP
The argument
.I 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
.I addr
parameter is determined by the domain in which the communication
is occurring.
The 
.I addrlen
is a value-result parameter; it should initially contain the
amount of space pointed to by
.IR 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.
.PP
It is possible to
.IR select (2)
a socket for the purposes of doing an
.I accept
by selecting it for read.
.SH "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.
.SH ERRORS
The \fIaccept\fP will fail if:
.TP 20
[EBADF]
The descriptor is invalid.
.TP 20
[ENOTSOCK]
The descriptor references a file, not a socket.
.TP 20
[EOPNOTSUPP]
The referenced socket is not of type SOCK_STREAM.
.TP 20
[EFAULT]
The \fIaddr\fP parameter is not in a writable part of the
user address space.
.TP 20
[EWOULDBLOCK]
The socket is marked non-blocking and no connections
are present to be accepted.
.SH SEE ALSO
bind(2), connect(2), listen(2), select(2), socket(2)
Commit	Line	Data
95f52c01 KM	1	.\" Copyright (c) 1983 Regents of the University of California.
	2	.\" All rights reserved. The Berkeley software License Agreement
	3	.\" specifies the terms and conditions for redistribution.
	4	.\"
95f51977	5	.\" @(#)accept.2 6.3 (Berkeley) 5/22/86
95f52c01	6	.\"
95f51977	7	.TH ACCEPT 2 "May 22, 1986"
95f52c01 KM	8	.UC 5
	9	.SH NAME
	10	accept \- accept a connection on a socket
	11	.SH SYNOPSIS
	12	.ft B
	13	.nf
	14	#include <sys/types.h>
	15	#include <sys/socket.h>
	16	.PP
	17	.ft B
	18	ns = accept(s, addr, addrlen)
	19	int ns, s;
	20	struct sockaddr *addr;
	21	int *addrlen;
	22	.fi
	23	.SH DESCRIPTION
	24	The argument
	25	.I s
a9f72a26	26	is a socket that has been created with
95f52c01 KM	27	.IR socket (2),
	28	bound to an address with
	29	.IR bind (2),
	30	and is listening for connections after a
	31	.IR listen (2).
	32	.I Accept
	33	extracts the first connection
	34	on the queue of pending connections, creates
	35	a new socket with the same properties of
	36	.I s
	37	and allocates a new file descriptor,
	38	.IR ns ,
	39	for the socket. If no pending connections are
	40	present on the queue, and the socket is not marked
	41	as non-blocking,
	42	.I accept
	43	blocks the caller until a connection is present.
	44	If the socket is marked non-blocking and no pending
	45	connections are present on the queue,
	46	.I accept
	47	returns an error as described below.
	48	The accepted socket,
	49	.IR ns ,
	50	may not be used
	51	to accept more connections. The original socket
	52	.I s
	53	remains open.
	54	.PP
	55	The argument
	56	.I addr
a9f72a26	57	is a result parameter that is filled in with
95f52c01 KM	58	the address of the connecting entity,
	59	as known to the communications layer.
	60	The exact format of the
	61	.I addr
	62	parameter is determined by the domain in which the communication
	63	is occurring.
	64	The
	65	.I addrlen
	66	is a value-result parameter; it should initially contain the
	67	amount of space pointed to by
	68	.IR addr ;
	69	on return it will contain the actual length (in bytes) of the
	70	address returned.
	71	This call
	72	is used with connection-based socket types, currently with SOCK_STREAM.
	73	.PP
	74	It is possible to
	75	.IR select (2)
	76	a socket for the purposes of doing an
	77	.I accept
	78	by selecting it for read.
	79	.SH "RETURN VALUE
bdad3a5a	80	The call returns \-1 on error. If it succeeds, it returns a non-negative
a9f72a26	81	integer that is a descriptor for the accepted socket.
95f52c01 KM	82	.SH ERRORS
	83	The \fIaccept\fP will fail if:
	84	.TP 20
	85	[EBADF]
	86	The descriptor is invalid.
	87	.TP 20
	88	[ENOTSOCK]
	89	The descriptor references a file, not a socket.
	90	.TP 20
	91	[EOPNOTSUPP]
	92	The referenced socket is not of type SOCK_STREAM.
	93	.TP 20
	94	[EFAULT]
	95	The \fIaddr\fP parameter is not in a writable part of the
	96	user address space.
	97	.TP 20
	98	[EWOULDBLOCK]
	99	The socket is marked non-blocking and no connections
	100	are present to be accepted.
	101	.SH SEE ALSO
	102	bind(2), connect(2), listen(2), select(2), socket(2)