2431275ac4
with NetBSD and the Single Unix Specification v2. This updates some structures with other, almost equivalent types and effort is under way to get the whole more consistent. Also removes a double definition of INET6 and some other clean-ups. Reviewed by: green, bde, phk Some part obtained from: NetBSD, SUSv2 specification
202 lines
5.6 KiB
Groff
202 lines
5.6 KiB
Groff
.\" Copyright (c) 1983, 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)accept.2 8.2 (Berkeley) 12/11/93
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.\" $FreeBSD$
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.\"
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.Dd December 11, 1993
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.Dt ACCEPT 2
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.Os BSD 4.2
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.Sh NAME
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.Nm accept
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.Nd accept a connection on a socket
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/socket.h>
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.Ft int
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.Fn accept "int s" "struct sockaddr *addr" "socklen_t *addrlen"
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.Sh DESCRIPTION
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The argument
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.Fa s
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is a socket that has been created with
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.Xr socket 2 ,
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bound to an address with
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.Xr bind 2 ,
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and is listening for connections after a
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.Xr listen 2 .
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The
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.Fn accept
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argument
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extracts the first connection request
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on the queue of pending connections, creates
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a new socket with the same properties of
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.Fa s
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and allocates a new file descriptor
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for the socket. If no pending connections are
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present on the queue, and the socket is not marked
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as non-blocking,
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.Fn accept
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blocks the caller until a connection is present.
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If the socket is marked non-blocking and no pending
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connections are present on the queue,
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.Fn accept
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returns an error as described below.
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The accepted socket
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may not be used
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to accept more connections. The original socket
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.Fa s
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remains open.
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.Pp
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The argument
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.Fa addr
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is a result parameter that is filled in with
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the address of the connecting entity,
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as known to the communications layer.
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The exact format of the
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.Fa addr
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parameter is determined by the domain in which the communication
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is occurring.
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The
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.Fa addrlen
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is a value-result parameter; it should initially contain the
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amount of space pointed to by
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.Fa addr ;
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on return it will contain the actual length (in bytes) of the
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address returned.
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This call
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is used with connection-based socket types, currently with
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.Dv SOCK_STREAM .
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.Pp
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It is possible to
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.Xr select 2
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a socket for the purposes of doing an
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.Fn accept
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by selecting it for read.
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.Pp
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For certain protocols which require an explicit confirmation,
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such as
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.Tn ISO
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or
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.Tn DATAKIT ,
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.Fn accept
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can be thought of
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as merely dequeueing the next connection
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request and not implying confirmation.
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Confirmation can be implied by a normal read or write on the new
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file descriptor, and rejection can be implied by closing the
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new socket.
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.Pp
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One can obtain user connection request data without confirming
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the connection by issuing a
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.Xr recvmsg 2
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call with an
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.Fa msg_iovlen
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of 0 and a non-zero
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.Fa msg_controllen ,
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or by issuing a
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.Xr getsockopt 2
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request.
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Similarly, one can provide user connection rejection information
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by issuing a
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.Xr sendmsg 2
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call with providing only the control information,
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or by calling
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.Xr setsockopt 2 .
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.Sh IMPLEMENTATION NOTES
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.Pp
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In the non-threaded library
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.Fn accept
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is implemented as the
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.Va accept
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syscall.
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.Pp
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In the threaded library, the
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.Va accept
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syscall is assembled to
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.Fn _thread_sys_accept
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and
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.Fn accept
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is implemented as a function which locks
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.Va s
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for read and write, then calls
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.Fn _thread_sys_accept .
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If the call to
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.Fn _thread_sys_accept
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would block, a context switch is performed. Before returning,
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.Fn accept
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unlocks
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.Va s .
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.Pp
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.Sh RETURN VALUES
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The call returns \-1 on error. If it succeeds, it returns a non-negative
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integer that is a descriptor for the accepted socket.
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.Sh ERRORS
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The
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.Fn accept
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will fail if:
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.Bl -tag -width EWOULDBLOCK
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.It Bq Er EBADF
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The descriptor is invalid.
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.It Bq Er EINTR
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The
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.Fn accept
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operation was interrupted.
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.It Bq Er EMFILE
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The per-process descriptor table is full.
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.It Bq Er ENFILE
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The system file table is full.
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.It Bq Er ENOTSOCK
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The descriptor references a file, not a socket.
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.It Bq Er EINVAL
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.Xr listen 2
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has not been called on the socket descriptor.
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.It Bq Er EFAULT
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The
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.Fa addr
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parameter is not in a writable part of the
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user address space.
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.It Bq Er EWOULDBLOCK
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The socket is marked non-blocking and no connections
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are present to be accepted.
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.El
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.Sh SEE ALSO
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.Xr bind 2 ,
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.Xr connect 2 ,
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.Xr getpeername 2 ,
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.Xr listen 2 ,
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.Xr select 2 ,
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.Xr socket 2
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.Sh HISTORY
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The
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.Fn accept
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function appeared in
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.Bx 4.2 .
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