.\" Copyright (c) 1983, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
+.\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 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.
+.\" %%%LICENSE_END
.\"
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified Oct 2003 by aeb
.\" Modified 2004-07-01 by mtk
.\"
-.TH SEND 2 2012-02-27 "Linux" "Linux Programmer's Manual"
+.TH SEND 2 2014-08-19 "Linux" "Linux Programmer's Manual"
.SH NAME
send, sendto, sendmsg \- send a message on a socket
.SH SYNOPSIS
The
.BR select (2)
call may be used to determine when it is possible to send more data.
-.PP
+.SS The flags argument
The
.I flags
argument is the bitwise OR
of zero or more of the following flags.
-.\" FIXME ? document MSG_PROXY (which went away in 2.3.15)
+.\" FIXME . ? document MSG_PROXY (which went away in 2.3.15)
.TP
-.BR MSG_CONFIRM " (Since Linux 2.3.15)"
+.BR MSG_CONFIRM " (since Linux 2.3.15)"
Tell the link layer that forward progress happened: you got a successful
reply from the other side.
If the link layer doesn't get this
.B SOCK_DGRAM
and
.B SOCK_RAW
-sockets and currently only implemented for IPv4 and IPv6.
+sockets and currently implemented only for IPv4 and IPv6.
See
.BR arp (7)
for details.
.TP
.B MSG_DONTROUTE
-Don't use a gateway to send out the packet, only send to hosts on
+Don't use a gateway to send out the packet, send to hosts only on
directly connected networks.
This is usually used only
by diagnostic or routing programs.
-This is only defined for protocol
+This is defined only for protocol
families that route; packet sockets don't.
.TP
.BR MSG_DONTWAIT " (since Linux 2.2)"
Terminates a record (when this notion is supported, as for sockets of type
.BR SOCK_SEQPACKET ).
.TP
-.BR MSG_MORE " (Since Linux 2.4.4)"
+.BR MSG_MORE " (since Linux 2.4.4)"
The caller has more data to send.
This flag is used with TCP sockets to obtain the same effect
as the
Since Linux 2.6, this flag is also supported for UDP sockets, and informs
the kernel to package all of the data sent in calls with this flag set
-into a single datagram which is only transmitted when a call is performed
+into a single datagram which is transmitted only when a call is performed
that does not specify this flag.
(See also the
.B UDP_CORK
the underlying protocol must also support
.I out-of-band
data.
-.PP
+.SS sendmsg()
The definition of the
.I msghdr
-structure follows.
-See
-.BR recv (2)
-and below for an exact description of its fields.
+structure employed by
+.BR sendmsg ()
+is as follows:
.in +4n
.nf
size_t msg_iovlen; /* # elements in msg_iov */
void *msg_control; /* ancillary data, see below */
size_t msg_controllen; /* ancillary data buffer len */
- int msg_flags; /* flags on received message */
+ int msg_flags; /* flags (unused) */
};
.fi
.in
.PP
+The
+.I msg_name
+field is used on an unconnected socket to specify the target
+address for a datagram.
+It points to a buffer containing the address; the
+.I msg_namelen
+field should be set to the size of the address.
+For a connected socket, these fields should be specified as NULL and 0,
+respectively.
+
+The
+.I msg_iov
+and
+.I msg_iovlen
+fields specify scatter-gather locations, as for
+.BR writev (2).
+
You may send control information using the
.I msg_control
and
.IR /proc/sys/net/core/optmem_max ;
see
.BR socket (7).
+
+The
+.I msg_flags
+field is ignored.
.\" Still to be documented:
.\" Send file descriptors and user credentials using the
.\" msg_control* fields.
-.\" The flags returned in msg_flags.
-.SH "RETURN VALUE"
-On success, these calls return the number of characters sent.
+.SH RETURN VALUE
+On success, these calls return the number of bytes sent.
On error, \-1 is returned, and
.I errno
is set appropriately.
the path prefix.
(See
.BR path_resolution (7).)
+.sp
+(For UDP sockets) An attempt was made to send to a
+network/broadcast address as though it was a unicast address.
.TP
.BR EAGAIN " or " EWOULDBLOCK
.\" Actually EAGAIN on Linux
and does not require these constants to have the same value,
so a portable application should check for both possibilities.
.TP
+.B EAGAIN
+(Internet domain datagram sockets)
+The socket referred to by
+.I sockfd
+had not previously been bound to an address and,
+upon attempting to bind it to an ephemeral port,
+it was determined that all port numbers in the ephemeral port range
+are currently in use.
+See the discussion of
+.I /proc/sys/net/ipv4/ip_local_port_range
+in
+.BR ip (7).
+.TP
.B EBADF
An invalid descriptor was specified.
.TP
.TP
.B EPIPE
The local end has been shut down on a connection oriented socket.
-In this case the process
+In this case, the process
will also receive a
.B SIGPIPE
unless
.B MSG_NOSIGNAL
is set.
-.SH "CONFORMING TO"
+.SH CONFORMING TO
4.4BSD, SVr4, POSIX.1-2001.
These function calls appeared in 4.2BSD.
.LP
-POSIX.1-2001 only describes the
+POSIX.1-2001 describes only the
.B MSG_OOB
and
.B MSG_EOR
.B MSG_CONFIRM
flag is a Linux extension.
.SH NOTES
-The prototypes given above follow the Single UNIX Specification,
-as glibc2 also does; the
-.I flags
-argument was \fIint\fP in 4.x BSD, but \fIunsigned int\fP in libc4 and libc5;
-the
-.I len
-argument was \fIint\fP in 4.x BSD and libc4, but \fIsize_t\fP in libc5;
-the
-.I addrlen
-argument was \fIint\fP in 4.x BSD and libc4 and libc5.
-See also
-.BR accept (2).
-
According to POSIX.1-2001, the
.I msg_controllen
field of the
.\" across architectures, but socklen_t is always 32 bits.
See
-.BR sendmmsg(2)
+.BR sendmmsg (2)
for information about a Linux-specific system call
that can be used to transmit multiple datagrams in a single call.
.SH BUGS
.BR sendto ()
is shown in
.BR getaddrinfo (3).
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR fcntl (2),
.BR getsockopt (2),
.BR recv (2),
.BR socket (7),
.BR tcp (7),
.BR udp (7)
+.SH COLOPHON
+This page is part of release 3.79 of the Linux
+.I man-pages
+project.
+A description of the project,
+information about reporting bugs,
+and the latest version of this page,
+can be found at
+\%http://www.kernel.org/doc/man\-pages/.
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