[unix-history] / usr / src / lib / libc / sys / accept.2

.\" Copyright (c) 1983 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms are permitted
.\" provided that the above copyright notice and this paragraph are
.\" duplicated in all such forms and that any documentation,
.\" advertising materials, and other materials related to such
.\" distribution and use acknowledge that the software was developed
.\" by the University of California, Berkeley.  The name of the
.\" University may not be used to endorse or promote products derived
.\" from this software without specific prior written permission.
.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
.\"
.\"	@(#)accept.2	6.4 (Berkeley) %G%
.\"
.TH ACCEPT 2 ""
.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
da268306 KB	1	.\" Copyright (c) 1983 The Regents of the University of California.
da268306 KB	2	.\" All rights reserved.
95f52c01	3	.\"
da268306 KB	4	.\" Redistribution and use in source and binary forms are permitted
	5	.\" provided that the above copyright notice and this paragraph are
	6	.\" duplicated in all such forms and that any documentation,
	7	.\" advertising materials, and other materials related to such
	8	.\" distribution and use acknowledge that the software was developed
	9	.\" by the University of California, Berkeley. The name of the
	10	.\" University may not be used to endorse or promote products derived
	11	.\" from this software without specific prior written permission.
	12	.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
	13	.\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
	14	.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
	15	.\"
	16	.\" @(#)accept.2 6.4 (Berkeley) %G%
95f52c01	17	.\"
f850922e	18	.TH ACCEPT 2 ""
95f52c01 KM	19	.UC 5
	20	.SH NAME
	21	accept \- accept a connection on a socket
	22	.SH SYNOPSIS
	23	.ft B
	24	.nf
	25	#include <sys/types.h>
	26	#include <sys/socket.h>
	27	.PP
	28	.ft B
	29	ns = accept(s, addr, addrlen)
	30	int ns, s;
	31	struct sockaddr *addr;
	32	int *addrlen;
	33	.fi
	34	.SH DESCRIPTION
	35	The argument
	36	.I s
a9f72a26	37	is a socket that has been created with
95f52c01 KM	38	.IR socket (2),
	39	bound to an address with
	40	.IR bind (2),
	41	and is listening for connections after a
	42	.IR listen (2).
	43	.I Accept
	44	extracts the first connection
	45	on the queue of pending connections, creates
	46	a new socket with the same properties of
	47	.I s
	48	and allocates a new file descriptor,
	49	.IR ns ,
	50	for the socket. If no pending connections are
	51	present on the queue, and the socket is not marked
	52	as non-blocking,
	53	.I accept
	54	blocks the caller until a connection is present.
	55	If the socket is marked non-blocking and no pending
	56	connections are present on the queue,
	57	.I accept
	58	returns an error as described below.
	59	The accepted socket,
	60	.IR ns ,
	61	may not be used
	62	to accept more connections. The original socket
	63	.I s
	64	remains open.
	65	.PP
	66	The argument
	67	.I addr
a9f72a26	68	is a result parameter that is filled in with
95f52c01 KM	69	the address of the connecting entity,
	70	as known to the communications layer.
	71	The exact format of the
	72	.I addr
	73	parameter is determined by the domain in which the communication
	74	is occurring.
	75	The
	76	.I addrlen
	77	is a value-result parameter; it should initially contain the
	78	amount of space pointed to by
	79	.IR addr ;
	80	on return it will contain the actual length (in bytes) of the
	81	address returned.
	82	This call
	83	is used with connection-based socket types, currently with SOCK_STREAM.
	84	.PP
	85	It is possible to
	86	.IR select (2)
	87	a socket for the purposes of doing an
	88	.I accept
	89	by selecting it for read.
	90	.SH "RETURN VALUE
bdad3a5a	91	The call returns \-1 on error. If it succeeds, it returns a non-negative
a9f72a26	92	integer that is a descriptor for the accepted socket.
95f52c01 KM	93	.SH ERRORS
	94	The \fIaccept\fP will fail if:
	95	.TP 20
	96	[EBADF]
	97	The descriptor is invalid.
	98	.TP 20
	99	[ENOTSOCK]
	100	The descriptor references a file, not a socket.
	101	.TP 20
	102	[EOPNOTSUPP]
	103	The referenced socket is not of type SOCK_STREAM.
	104	.TP 20
	105	[EFAULT]
	106	The \fIaddr\fP parameter is not in a writable part of the
	107	user address space.
	108	.TP 20
	109	[EWOULDBLOCK]
	110	The socket is marked non-blocking and no connections
	111	are present to be accepted.
	112	.SH SEE ALSO
	113	bind(2), connect(2), listen(2), select(2), socket(2)