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	1	.\" $NetBSD: send.2,v 1.6 1996/01/15 01:17:18 thorpej Exp $
	2	.\"
	3	.\" Copyright (c) 1983, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)send.2 8.2 (Berkeley) 2/21/94
	35	.\"
	36	.Dd February 21, 1994
	37	.Dt SEND 2
	38	.Os BSD 4.2
	39	.Sh NAME
	40	.Nm send ,
	41	.Nm sendto ,
	42	.Nm sendmsg
	43	.Nd send a message from a socket
	44	.Sh SYNOPSIS
	45	.Fd #include <sys/types.h>
	46	.Fd #include <sys/socket.h>
	47	.Ft ssize_t
	48	.Fn send "int s" "const void *msg" "size_t len" "int flags"
	49	.Ft ssize_t
	50	.Fn sendto "int s" "const void msg" "size_t len" "int flags" "const struct sockaddr to" "socklen_t tolen"
	51	.Ft ssize_t
	52	.Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
	53	.Sh DESCRIPTION
	54	.Fn Send ,
	55	.Fn sendto ,
	56	and
	57	.Fn sendmsg
	58	are used to transmit a message to another socket.
	59	.Fn Send
	60	may be used only when the socket is in a
	61	.Em connected
	62	state, while
	63	.Fn sendto
	64	and
	65	.Fn sendmsg
	66	may be used at any time.
	67	.Pp
	68	The address of the target is given by
	69	.Fa to
	70	with
	71	.Fa tolen
	72	specifying its size.
	73	The length of the message is given by
	74	.Fa len .
	75	If the message is too long to pass atomically through the
	76	underlying protocol, the error
	77	.Er EMSGSIZE
	78	is returned, and
	79	the message is not transmitted.
	80	.Pp
	81	No indication of failure to deliver is implicit in a
	82	.Fn send .
	83	Locally detected errors are indicated by a return value of -1.
	84	.Pp
	85	If no messages space is available at the socket to hold
	86	the message to be transmitted, then
	87	.Fn send
	88	normally blocks, unless the socket has been placed in
	89	non-blocking I/O mode.
	90	The
	91	.Xr select 2
	92	call may be used to determine when it is possible to
	93	send more data.
	94	.Pp
	95	The
	96	.Fa flags
	97	parameter may include one or more of the following:
	98	.Bd -literal
	99	#define MSG_OOB 0x1 /* process out-of-band data */
	100	#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
	101	.Ed
	102	.Pp
	103	The flag
	104	.Dv MSG_OOB
	105	is used to send
	106	.Dq out-of-band
	107	data on sockets that support this notion (e.g.
	108	.Dv SOCK_STREAM ) ;
	109	the underlying protocol must also support
	110	.Dq out-of-band
	111	data.
	112	.Dv MSG_DONTROUTE
	113	is usually used only by diagnostic or routing programs.
	114	.Pp
	115	See
	116	.Xr recv 2
	117	for a description of the
	118	.Fa msghdr
	119	structure.
	120	.Sh RETURN VALUES
	121	The call returns the number of characters sent, or -1
	122	if an error occurred.
	123	.Sh ERRORS
	124	.Fn Send ,
	125	.Fn sendto ,
	126	and
	127	.Fn sendmsg
	128	fail if:
	129	.Bl -tag -width Er
	130	.It Bq Er EBADF
	131	An invalid descriptor was specified.
	132	.It Bq Er ENOTSOCK
	133	The argument
	134	.Fa s
	135	is not a socket.
	136	.It Bq Er EFAULT
	137	An invalid user space address was specified for a parameter.
	138	.It Bq Er EMSGSIZE
	139	The socket requires that message be sent atomically,
	140	and the size of the message to be sent made this impossible.
	141	.It Bq Er EAGAIN
	142	The socket is marked non-blocking and the requested operation
	143	would block.
	144	.It Bq Er ENOBUFS
	145	The system was unable to allocate an internal buffer.
	146	The operation may succeed when buffers become available.
	147	.It Bq Er ENOBUFS
	148	The output queue for a network interface was full.
	149	This generally indicates that the interface has stopped sending,
	150	but may be caused by transient congestion.
	151	.It Bq Er EACCES
	152	The SO_BROADCAST option is not set on the socket, and a broadcast address
	153	was given as the destination.
	154	.It Bq Er EHOSTUNREACH
	155	The destination address specified an unreachable host.
	156	.El
	157	.Sh SEE ALSO
	158	.Xr fcntl 2 ,
	159	.Xr recv 2 ,
	160	.Xr select 2 ,
	161	.Xr getsockopt 2 ,
	162	.Xr socket 2 ,
	163	.Xr write 2
	164	.Sh HISTORY
	165	The
	166	.Fn send
	167	function call appeared in
	168	.Bx 4.2 .