1.\" $NetBSD: send.2,v 1.25 2004/05/13 10:20:58 wiz 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)send.2 8.2 (Berkeley) 2/21/94 31.\" 32.Dd April 20, 2003 33.Dt SEND 2 34.Os 35.Sh NAME 36.Nm send , 37.Nm sendto , 38.Nm sendmsg 39.Nd send a message from a socket 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In sys/socket.h 44.Ft ssize_t 45.Fn send "int s" "const void *msg" "size_t len" "int flags" 46.Ft ssize_t 47.Fn sendto "int s" "const void *msg" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen" 48.Ft ssize_t 49.Fn sendmsg "int s" "const struct msghdr *msg" "int flags" 50.Sh DESCRIPTION 51.Fn send , 52.Fn sendto , 53and 54.Fn sendmsg 55are used to transmit a message to another socket. 56.Fn send 57may be used only when the socket is in a 58.Em connected 59state, while 60.Fn sendto 61and 62.Fn sendmsg 63may be used at any time. 64.Pp 65The address of the target is given by 66.Fa to 67with 68.Fa tolen 69specifying its size. 70The length of the message is given by 71.Fa len . 72If the message is too long to pass atomically through the 73underlying protocol, the error 74.Er EMSGSIZE 75is returned, and 76the message is not transmitted. 77.Pp 78No indication of failure to deliver is implicit in a 79.Fn send . 80Locally detected errors are indicated by a return value of \-1. 81.Pp 82If no messages space is available at the socket to hold 83the message to be transmitted, then 84.Fn send 85normally blocks, unless the socket has been placed in 86non-blocking I/O mode. 87The 88.Xr select 2 89or 90.Xr poll 2 91call may be used to determine when it is possible to 92send more data. 93.Pp 94The 95.Fa flags 96parameter may include one or more of the following: 97.Bd -literal 98#define MSG_OOB 0x1 /* process out-of-band data */ 99#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */ 100.Ed 101.Pp 102The flag 103.Dv MSG_OOB 104is used to send 105.Dq out-of-band 106data on sockets that support this notion (e.g. 107.Dv SOCK_STREAM ) ; 108the underlying protocol must also support 109.Dq out-of-band 110data. 111.Dv MSG_DONTROUTE 112is usually used only by diagnostic or routing programs. 113.Pp 114See 115.Xr recv 2 116for a description of the 117.Fa msghdr 118structure. 119.Sh RETURN VALUES 120The call returns the number of characters sent, or \-1 121if an error occurred. 122.Sh ERRORS 123.Fn send , 124.Fn sendto , 125and 126.Fn sendmsg 127fail if: 128.Bl -tag -width Er 129.It Bq Er EBADF 130An invalid descriptor was specified. 131.It Bq Er ENOTSOCK 132The argument 133.Fa s 134is not a socket. 135.It Bq Er EFAULT 136An invalid user space address was specified for a parameter. 137.It Bq Er EMSGSIZE 138The socket requires that message be sent atomically, 139and the size of the message to be sent made this impossible. 140.It Bq Er EAGAIN 141The socket is marked non-blocking and the requested operation 142would block. 143.It Bq Er ENOBUFS 144The system was unable to allocate an internal buffer. 145The operation may succeed when buffers become available. 146.It Bq Er ENOBUFS 147The output queue for a network interface was full. 148This generally indicates that the interface has stopped sending, 149but may be caused by transient congestion. 150.It Bq Er EACCES 151The SO_BROADCAST option is not set on the socket, and a broadcast address 152was given as the destination. 153.It Bq Er EHOSTUNREACH 154The destination for the message is unreachable. 155.It Bq Er EINVAL 156The total length of the I/O is more than can be expressed by the ssize_t 157return value. 158.It Bq Er EAFNOSUPPORT 159Addresses in the specified address family cannot be used with this socket. 160.El 161.Pp 162.Fn sendto 163will also fail if: 164.Bl -tag -width Er 165.It Bq Er EISCONN 166A destination address was specified and the socket is already connected. 167.El 168.Pp 169.Fn sendmsg 170will also fail if: 171.Bl -tag -width Er 172.It Bq Er EMSGSIZE 173The 174.Fa msg_iovlen 175member of the 176.Fa msg 177structure is less than or equal to 0 178or is greater than 179.Dv {IOV_MAX} . 180.El 181.Sh SEE ALSO 182.Xr fcntl 2 , 183.Xr getsockopt 2 , 184.Xr recv 2 , 185.Xr select 2 , 186.Xr socket 2 , 187.Xr write 2 188.Sh HISTORY 189The 190.Fn send 191function call appeared in 192.Bx 4.2 . 193