202 lines
5.6 KiB
Groff
202 lines
5.6 KiB
Groff
.\" Copyright (c) 1983, 1990, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)accept.2 8.2 (Berkeley) 12/11/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 11, 1993
|
|
.Dt ACCEPT 2
|
|
.Os BSD 4.2
|
|
.Sh NAME
|
|
.Nm accept
|
|
.Nd accept a connection on a socket
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/types.h>
|
|
.Fd #include <sys/socket.h>
|
|
.Ft int
|
|
.Fn accept "int s" "struct sockaddr *addr" "int *addrlen"
|
|
.Sh DESCRIPTION
|
|
The argument
|
|
.Fa s
|
|
is a socket that has been created with
|
|
.Xr socket 2 ,
|
|
bound to an address with
|
|
.Xr bind 2 ,
|
|
and is listening for connections after a
|
|
.Xr listen 2 .
|
|
The
|
|
.Fn accept
|
|
argument
|
|
extracts the first connection request
|
|
on the queue of pending connections, creates
|
|
a new socket with the same properties of
|
|
.Fa 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,
|
|
.Fn 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,
|
|
.Fn accept
|
|
returns an error as described below.
|
|
The accepted socket
|
|
may not be used
|
|
to accept more connections. The original socket
|
|
.Fa s
|
|
remains open.
|
|
.Pp
|
|
The argument
|
|
.Fa 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
|
|
.Fa addr
|
|
parameter is determined by the domain in which the communication
|
|
is occurring.
|
|
The
|
|
.Fa addrlen
|
|
is a value-result parameter; it should initially contain the
|
|
amount of space pointed to by
|
|
.Fa 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
|
|
.Dv SOCK_STREAM .
|
|
.Pp
|
|
It is possible to
|
|
.Xr select 2
|
|
a socket for the purposes of doing an
|
|
.Fn accept
|
|
by selecting it for read.
|
|
.Pp
|
|
For certain protocols which require an explicit confirmation,
|
|
such as
|
|
.Tn ISO
|
|
or
|
|
.Tn DATAKIT ,
|
|
.Fn accept
|
|
can be thought of
|
|
as merely dequeueing 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.
|
|
.Pp
|
|
One can obtain user connection request data without confirming
|
|
the connection by issuing a
|
|
.Xr recvmsg 2
|
|
call with an
|
|
.Fa msg_iovlen
|
|
of 0 and a non-zero
|
|
.Fa msg_controllen ,
|
|
or by issuing a
|
|
.Xr getsockopt 2
|
|
request.
|
|
Similarly, one can provide user connection rejection information
|
|
by issuing a
|
|
.Xr sendmsg 2
|
|
call with providing only the control information,
|
|
or by calling
|
|
.Xr setsockopt 2 .
|
|
.Sh IMPLEMENTATION NOTES
|
|
.Pp
|
|
In the non-threaded library
|
|
.Fn accept
|
|
is implemented as the
|
|
.Va accept
|
|
syscall.
|
|
.Pp
|
|
In the threaded library, the
|
|
.Va accept
|
|
syscall is assembled to
|
|
.Fn _thread_sys_accept
|
|
and
|
|
.Fn accept
|
|
is implemented as a function which locks
|
|
.Va s
|
|
for read and write, then calls
|
|
.Fn _thread_sys_accept .
|
|
If the call to
|
|
.Fn _thread_sys_accept
|
|
would block, a context switch is performed. Before returning,
|
|
.Fn accept
|
|
unlocks
|
|
.Va s .
|
|
.Pp
|
|
.Sh 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.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn accept
|
|
will fail if:
|
|
.Bl -tag -width EWOULDBLOCK
|
|
.It Bq Er EBADF
|
|
The descriptor is invalid.
|
|
.It Bq Er EINTR
|
|
The
|
|
.Fn accept
|
|
operation was interrupted.
|
|
.It Bq Er EMFILE
|
|
The per-process descriptor table is full.
|
|
.It Bq Er ENFILE
|
|
The system file table is full.
|
|
.It Bq Er ENOTSOCK
|
|
The descriptor references a file, not a socket.
|
|
.It Bq Er EINVAL
|
|
.Xr listen 2
|
|
has not been called on the socket descriptor.
|
|
.It Bq Er EFAULT
|
|
The
|
|
.Fa addr
|
|
parameter is not in a writable part of the
|
|
user address space.
|
|
.It Bq Er EWOULDBLOCK
|
|
The socket is marked non-blocking and no connections
|
|
are present to be accepted.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr bind 2 ,
|
|
.Xr connect 2 ,
|
|
.Xr getpeername 2 ,
|
|
.Xr listen 2 ,
|
|
.Xr select 2 ,
|
|
.Xr socket 2
|
|
.Sh HISTORY
|
|
The
|
|
.Fn accept
|
|
function appeared in
|
|
.Bx 4.2 .
|