.\" $NetBSD: send.2,v 1.6 1996/01/15 01:17:18 thorpej Exp $ .\" .\" Copyright (c) 1983, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)send.2 8.2 (Berkeley) 2/21/94 .\" .Dd February 21, 1994 .Dt SEND 2 .Os BSD 4.2 .Sh NAME .Nm send , .Nm sendto , .Nm sendmsg .Nd send a message from a socket .Sh SYNOPSIS .Fd #include <sys/types.h> .Fd #include <sys/socket.h> .Ft ssize_t .Fn send "int s" "const void *msg" "size_t len" "int flags" .Ft ssize_t .Fn sendto "int s" "const void *msg" "size_t len" "int flags" "const struct sockaddr *to" "int tolen" .Ft ssize_t .Fn sendmsg "int s" "const struct msghdr *msg" "int flags" .Sh DESCRIPTION .Fn Send , .Fn sendto , and .Fn sendmsg are used to transmit a message to another socket. .Fn Send may be used only when the socket is in a .Em connected state, while .Fn sendto and .Fn sendmsg may be used at any time. .Pp The address of the target is given by .Fa to with .Fa tolen specifying its size. The length of the message is given by .Fa len . If the message is too long to pass atomically through the underlying protocol, the error .Er EMSGSIZE is returned, and the message is not transmitted. .Pp No indication of failure to deliver is implicit in a .Fn send . Locally detected errors are indicated by a return value of -1. .Pp If no messages space is available at the socket to hold the message to be transmitted, then .Fn send normally blocks, unless the socket has been placed in non-blocking I/O mode. The .Xr select 2 call may be used to determine when it is possible to send more data. .Pp The .Fa flags parameter may include one or more of the following: .Bd -literal #define MSG_OOB 0x1 /* process out-of-band data */ #define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */ .Ed .Pp The flag .Dv MSG_OOB is used to send .Dq out-of-band data on sockets that support this notion (e.g. .Dv SOCK_STREAM ) ; the underlying protocol must also support .Dq out-of-band data. .Dv MSG_DONTROUTE is usually used only by diagnostic or routing programs. .Pp See .Xr recv 2 for a description of the .Fa msghdr structure. .Sh RETURN VALUES The call returns the number of characters sent, or -1 if an error occurred. .Sh ERRORS .Fn Send , .Fn sendto , and .Fn sendmsg fail if: .Bl -tag -width Er .It Bq Er EBADF An invalid descriptor was specified. .It Bq Er ENOTSOCK The argument .Fa s is not a socket. .It Bq Er EFAULT An invalid user space address was specified for a parameter. .It Bq Er EMSGSIZE The socket requires that message be sent atomically, and the size of the message to be sent made this impossible. .It Bq Er EAGAIN The socket is marked non-blocking and the requested operation would block. .It Bq Er ENOBUFS The system was unable to allocate an internal buffer. The operation may succeed when buffers become available. .It Bq Er ENOBUFS The output queue for a network interface was full. This generally indicates that the interface has stopped sending, but may be caused by transient congestion. .It Bq Er EACCES The SO_BROADCAST option is not set on the socket, and a broadcast address was given as the destination. .It Bq Er EHOSTUNREACH The destination address specified an unreachable host. .El .Sh SEE ALSO .Xr fcntl 2 , .Xr recv 2 , .Xr select 2 , .Xr getsockopt 2 , .Xr socket 2 , .Xr write 2 .Sh HISTORY The .Fn send function call appeared in .Bx 4.2 .