1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)send.2 6.9 (Berkeley) 5/1/91 33.\" $Id: send.2,v 1.4 1993/11/29 21:25:33 jtc Exp $ 34.\" 35.Dd May 1, 1991 36.Dt SEND 2 37.Os BSD 4.2 38.Sh NAME 39.Nm send , 40.Nm sendto , 41.Nm sendmsg 42.Nd send a message from a socket 43.Sh SYNOPSIS 44.Fd #include <sys/types.h> 45.Fd #include <sys/socket.h> 46.Ft int 47.Fn send "int s" "const void *msg" "int len" "int flags" 48.Ft int 49.Fn sendto "int s" "const void *msg" "int len" "int flags" "const struct sockaddr *to" "int tolen" 50.Ft int 51.Fn sendmsg "int s" "const struct msghdr *msg" "int flags" 52.Sh DESCRIPTION 53.Fn Send , 54.Fn sendto , 55and 56.Fn sendmsg 57are used to transmit a message to another socket. 58.Fn Send 59may be used only when the socket is in a 60.Em connected 61state, while 62.Fn sendto 63and 64.Fn sendmsg 65may be used at any time. 66.Pp 67The address of the target is given by 68.Fa to 69with 70.Fa tolen 71specifying its size. 72The length of the message is given by 73.Fa len . 74If the message is too long to pass atomically through the 75underlying protocol, the error 76.Er EMSGSIZE 77is returned, and 78the message is not transmitted. 79.Pp 80No indication of failure to deliver is implicit in a 81.Fn send . 82Locally detected errors are indicated by a return value of -1. 83.Pp 84If no messages space is available at the socket to hold 85the message to be transmitted, then 86.Fn send 87normally blocks, unless the socket has been placed in 88non-blocking I/O mode. 89The 90.Xr select 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 EWOULDBLOCK 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.El 151.Sh SEE ALSO 152.Xr fcntl 2 , 153.Xr recv 2 , 154.Xr select 2 , 155.Xr getsockopt 2 , 156.Xr socket 2 , 157.Xr write 2 158.Sh HISTORY 159The 160.Fn send 161function call appeared in 162.Bx 4.2 . 163