1.\" $NetBSD: send.2,v 1.13 1999/02/10 18:20:03 kleink 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 , 56and 57.Fn sendmsg 58are used to transmit a message to another socket. 59.Fn send 60may be used only when the socket is in a 61.Em connected 62state, while 63.Fn sendto 64and 65.Fn sendmsg 66may be used at any time. 67.Pp 68The address of the target is given by 69.Fa to 70with 71.Fa tolen 72specifying its size. 73The length of the message is given by 74.Fa len . 75If the message is too long to pass atomically through the 76underlying protocol, the error 77.Er EMSGSIZE 78is returned, and 79the message is not transmitted. 80.Pp 81No indication of failure to deliver is implicit in a 82.Fn send . 83Locally detected errors are indicated by a return value of -1. 84.Pp 85If no messages space is available at the socket to hold 86the message to be transmitted, then 87.Fn send 88normally blocks, unless the socket has been placed in 89non-blocking I/O mode. 90The 91.Xr select 2 92or 93.Xr poll 2 94call may be used to determine when it is possible to 95send more data. 96.Pp 97The 98.Fa flags 99parameter may include one or more of the following: 100.Bd -literal 101#define MSG_OOB 0x1 /* process out-of-band data */ 102#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */ 103.Ed 104.Pp 105The flag 106.Dv MSG_OOB 107is used to send 108.Dq out-of-band 109data on sockets that support this notion (e.g. 110.Dv SOCK_STREAM ) ; 111the underlying protocol must also support 112.Dq out-of-band 113data. 114.Dv MSG_DONTROUTE 115is usually used only by diagnostic or routing programs. 116.Pp 117See 118.Xr recv 2 119for a description of the 120.Fa msghdr 121structure. 122.Sh RETURN VALUES 123The call returns the number of characters sent, or -1 124if an error occurred. 125.Sh ERRORS 126.Fn send , 127.Fn sendto , 128and 129.Fn sendmsg 130fail if: 131.Bl -tag -width Er 132.It Bq Er EBADF 133An invalid descriptor was specified. 134.It Bq Er ENOTSOCK 135The argument 136.Fa s 137is not a socket. 138.It Bq Er EFAULT 139An invalid user space address was specified for a parameter. 140.It Bq Er EMSGSIZE 141The socket requires that message be sent atomically, 142and the size of the message to be sent made this impossible. 143.It Bq Er EAGAIN 144The socket is marked non-blocking and the requested operation 145would block. 146.It Bq Er ENOBUFS 147The system was unable to allocate an internal buffer. 148The operation may succeed when buffers become available. 149.It Bq Er ENOBUFS 150The output queue for a network interface was full. 151This generally indicates that the interface has stopped sending, 152but may be caused by transient congestion. 153.It Bq Er EACCES 154The SO_BROADCAST option is not set on the socket, and a broadcast address 155was given as the destination. 156.It Bq Er EHOSTUNREACH 157The destination for the message is unreachable. 158.It Bq Er EINVAL 159The total length of the I/O is more than can be expressed by the ssize_t 160return value. 161.It Bq Er EAFNOSUPPORT 162Addresses in the specified address family cannot be used with this socket. 163.El 164.Pp 165.Fn sendmsg 166will also fail if: 167.Bl -tag -width Er 168.It Bq Er EMSGSIZE 169The 170.Fa msg_iovlen 171member of the 172.Fa msg 173structure is less than or equal to 0 174or is greater than 175.Dv {IOV_MAX} . 176.El 177.Sh SEE ALSO 178.Xr fcntl 2 , 179.Xr recv 2 , 180.Xr select 2 , 181.Xr getsockopt 2 , 182.Xr socket 2 , 183.Xr write 2 184.Sh HISTORY 185The 186.Fn send 187function call appeared in 188.Bx 4.2 . 189