316 lines
8.5 KiB
Groff
316 lines
8.5 KiB
Groff
.\" $NetBSD: send.2,v 1.6 1996/01/15 01:17:18 thorpej Exp $
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.\"
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.\" Copyright (c) 1983, 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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.\" @(#)send.2 8.2 (Berkeley) 2/21/94
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.\"
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.Dd February 21, 1994
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.Dt SEND 2
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.Os BSD 4.2
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.Sh NAME
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.Nm send ,
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.Nm sendmsg ,
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.Nm sendto
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.Nd send a message from a socket
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.Sh SYNOPSIS
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.Fd #include <sys/socket.h>
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.Ft ssize_t
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.Fo send
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.Fa "int socket"
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.Fa "const void *buffer"
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.Fa "size_t length"
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.Fa "int flags"
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.Fc
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.Ft ssize_t
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.Fo sendmsg
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.Fa "int socket"
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.Fa "const struct msghdr *message"
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.Fa "int flags"
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.Fc
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.Ft ssize_t
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.Fo sendto
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.Fa "int socket"
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.Fa "const void *buffer"
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.Fa "size_t length"
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.Fa "int flags"
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.Fa "const struct sockaddr *dest_addr"
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.Fa "socklen_t dest_len"
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.Fc
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.Sh DESCRIPTION
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.Fn send ,
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.Fn sendto ,
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and
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.Fn sendmsg
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are used to transmit a message to another socket.
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.Fn send
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may be used only when the socket is in a
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.Em connected
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state, while
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.Fn sendto
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and
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.Fn sendmsg
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may be used at any time.
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.Pp
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The address of the target is given by
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.Fa dest_addr
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with
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.Fa dest_len
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specifying its size.
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The length of the message is given by
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.Fa length .
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If the message is too long to pass atomically through the
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underlying protocol, the error
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.Er EMSGSIZE
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is returned, and
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the message is not transmitted.
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.Pp
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No indication of failure to deliver is implicit in a
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.Fn send .
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Locally detected errors are indicated by a return value of -1.
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.Pp
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If no messages space is available at the socket to hold
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the message to be transmitted, then
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.Fn send
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normally blocks, unless the socket has been placed in
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non-blocking I/O mode.
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The
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.Xr select 2
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call may be used to determine when it is possible to
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send more data.
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.Pp
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The
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.Fa flags
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parameter may include one or more of the following:
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.Bd -literal
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#define MSG_OOB 0x1 /* process out-of-band data */
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#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
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.Ed
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.Pp
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The flag
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.Dv MSG_OOB
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is used to send
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.Dq out-of-band
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data on sockets that support this notion (e.g.
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.Dv SOCK_STREAM ) ;
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the underlying protocol must also support
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.Dq out-of-band
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data.
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.Dv MSG_DONTROUTE
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is usually used only by diagnostic or routing programs.
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.Pp
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The
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.Fn sendmsg
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system call uses a
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.Fa msghdr
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structure to minimize the number of directly supplied arguments.
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The
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.Fa msg_iov
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and
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.Fa msg_iovlen
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fields of message specify zero or more buffers
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containing the data to be sent.
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.Fa msg_iov
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points to an array of iovec structures;
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.Fa msg_iovlen
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shall be set to the dimension of this array.
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In each iovec structure, the
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.Fa iov_base
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field specifies a storage area and
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the
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.Fa iov_len
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field gives its size in bytes. Some of these sizes can be zero.
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The data from each storage area indicated by
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.Fa msg_iov
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is sent in turn.
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See
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.Xr recv 2
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for a complete description of the
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.Fa msghdr
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structure.
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.Sh RETURN VALUES
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Upon successful completion,
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the number of bytes which were sent is returned.
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Otherwise, -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The
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.Fn send ,
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.Fn sendmsg ,
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and
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.Fn sendto
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system calls will fail if:
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.Bl -tag -width Er
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.\" ===========
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.It Bq Er EACCES
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The SO_BROADCAST option is not set on the socket
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and a broadcast address is given as the destination.
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.\" ===========
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.It Bq Er EAGAIN
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The socket is marked non-blocking
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and the requested operation would block.
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.\" ===========
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.It Bq Er EBADF
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An invalid descriptor is specified.
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.\" ===========
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.It Bq Er ECONNRESET
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A connection is forcibly closed by a peer.
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.\" ===========
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.It Bq Er EFAULT
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An invalid user space address is specified for a parameter.
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.\" ===========
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.It Bq Er EHOSTUNREACH
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The destination address specifies an unreachable host.
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.\" ===========
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.It Bq Er EINTR
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A signal interrupts the system call
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before any data is transmitted.
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.\" ===========
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.It Bq Er EMSGSIZE
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The socket requires that message be sent atomically,
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and the size of the message to be sent makes this impossible.
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.Dv IOV_MAX .
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.\" ===========
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.It Bq Er ENETDOWN
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The local network interface used to reach the destination is down.
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.\" ===========
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.It Bq Er ENETUNREACH
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No route to the network is present.
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.\" ===========
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.It Bq Er ENOBUFS
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The system is unable to allocate an internal buffer.
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The operation may succeed when buffers become available.
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.\" ===========
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.It Bq Er ENOBUFS
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The output queue for a network interface is full.
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This generally indicates that the interface has stopped sending,
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but may be caused by transient congestion.
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.\" ===========
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.It Bq Er ENOTSOCK
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The argument
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.Fa socket
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is not a socket.
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.\" ===========
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.It Bq Er EOPNOTSUPP
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.Fa socket
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does not support (some of) the option(s) specified in
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.Fa flags .
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.\" ===========
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.It Bq Er EPIPE
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The socket is shut down for writing
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or the socket is connection-mode and is no longer connected.
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In the latter case, and if the socket is of type SOCK_STREAM,
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the SIGPIPE signal is generated to the calling thread.
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.\" ==========
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.It Bq Er EADDRNOTAVAIL
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The specified address is not available or no longer available on this machine.
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.El
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.Pp
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The
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.Fn sendmsg
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and
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.Fn sendto
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system calls will fail if:
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.Bl -tag -width Er
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.\" ===========
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.It Bq Er EAFNOSUPPORT
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Addresses in the specified address family cannot be used
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with this socket.
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.\" ===========
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.It Bq Er EDESTADDRREQ
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The socket is not connection-mode and does not have its peer address set,
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and no destination address is specified.
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.\" ===========
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.It Bq Er EISCONN
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A destination address was specified and the socket is already connected.
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.\" ===========
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.It Bq Er ENOENT
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A component of the pathname does not name an existing file
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or the path name is an empty string.
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.\" ===========
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.It Bq Er ENOMEM
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Insufficient memory is available to fulfill the request.
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.\" ===========
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.It Bq Er ENOTCONN
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The socket is connection-mode, but is not connected.
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.\" ===========
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.It Bq Er ENOTDIR
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A component of the path prefix of the pathname in the socket address
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is not a directory.
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.El
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.Pp
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The
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.Fn send
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system call will fail if:
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.Bl -tag -width Er
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.\" ===========
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.It Bq Er EDESTADDRREQ
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The socket is not connection-mode and no peer address is set.
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.\" ===========
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.It Bq Er ENOTCONN
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The socket is not connected or otherwise has not had the peer pre-specified.
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.El
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.Pp
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The
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.Fn sendmsg
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system call will fail if:
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.Bl -tag -width Er
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.\" ===========
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.It Bq Er EINVAL
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The sum of the iov_len values overflows an ssize_t.
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.\" ===========
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.It Bq Er EMSGSIZE
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The socket requires that message be sent atomically,
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and the size of the message to be sent makes this impossible,
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or the msg_iovlen member of the msghdr structure pointed to by message
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is less than or equal to 0 or is greater than
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.Dv IOV_MAX .
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.El
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.Sh LEGACY SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/socket.h>
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.Pp
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The include file
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.In sys/types.h is necessary.
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.Sh SEE ALSO
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.Xr fcntl 2 ,
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.Xr getsockopt 2 ,
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.Xr recv 2 ,
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.Xr select 2 ,
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.Xr socket 2 ,
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.Xr write 2 ,
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.Xr compat 5
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.Sh HISTORY
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The
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.Fn send
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function call appeared in
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.Bx 4.2 .
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