sendto.3.man

This a separate release of the OpenSS7 X/Open XTI/TLI library, TLI modules (timod, tirdwr) and the I

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.TH SENDTO 3 "2004/05/16 02:35:35" "strxnet-0_9_2-4" "Linux Fast-STREAMS Sockets Library"
.SH NAME
.B sendto
\- send a message on a socket
.SH SYNOPSIS
.PP
.B #include <sys/socket.h>
.HP
.BI "ssize_t sendto(int " socket ", const void *" message ", size_t " length ", int " flags ", const struct sockaddr *" dest_addr ", socklen_t " dest_len );
.SH DESCRIPTION
.PP
The
.BR sendto ()
function sends a message through a connection-mode or
connectionless-mode socket.  If the socket is connectionless-mode,
the message will be sent to the address specified by
.IR dest_addr .
If
the socket is connection-mode,
.I dest_addr
is ignored.
.PP
The function takes the following arguments:
.TP
.I socket
Specifies the socket file descriptor.
.TP
.I message
Points to a buffer containing the message to be sent.
.TP
.I length
Specifies the size of the message in bytes.
.TP
.I flags
Specifies the type of message transmission.  Values of this
argument are formed by logically OR'ing zero or more of the
following flags:
.RS
.TP
.B MSG_EOR
Terminates a record (if supported by the protocol)
.TP
.B MSG_OOB
Sends out-of-band data on sockets that support out-of-band
data.  The significance and semantics of out-of-band data
are protocol-specific.
.RE
.TP
.I dest_addr
Points to a
.B sockaddr
structure containing the destination
address.  The length and format of the address depend on the
address family of the socket.
.TP
.I dest_len
Specifies the length of the
.B sockaddr
structure pointed to by
the
.I dest_addr
argument.
.PP
If the socket protocol supports broadcast and the specified address
is a broadcast address for the socket protocol,
.BR sendto ()
will fail
if the
.B SO_BROADCAST
option is not set for the socket.
.PP
The
.I dest_addr
argument specifies the address of the target.  The
length argument specifies the length of the message.
.PP
Successful completion of a call to
.BR sendto ()
does not guarantee
delivery of the message.  A return value of -1 indicates only
locally-detected errors.
.PP
If space is not available at the sending socket to hold the message
to be transmitted and the socket file descriptor does not have
.B O_NONBLOCK
set,
.BR sendto ()
blocks until space is available.  If space
is not available at the sending socket to hold the message to be
transmitted and the socket file descriptor does have
.B O_NONBLOCK
set,
.BR sendto ()
will fail.
.PP
The socket in use may require the process to have appropriate
privileges to use the
.BR sendto ()
function.
.SH NOTES
.PP
The
.BR select (2)
and
.BR poll (2)
functions can be used to determine
when it is possible to send more data.
.SH CAVEATS
.PP
This system call is implemented as a
.B SIOCSOCKSYS
IOCTL.  See
.BR socksys (4)
for more information.
.SH "RETURN VALUE"
.PP
Upon successful completion,
.BR sendto ()
returns the number of bytes
sent.  Otherwise, -1 is returned and errno is set to indicate the
error.
.SH ERRORS
.PP
The
.BR sendto ()
function will fail if:
.TP
.RB [ EAFNOSUPPORT ]
Addresses in the specified address family cannot be used with
this socket.
.TP
.RB [ EAGAIN "] or [" EWOULDBLOCK ]
The socket's file descriptor is marked
.B O_NONBLOCK
and the
requested operation would block.
.TP
.RB [ EBADF ]
The
.I socket
argument is not a valid file descriptor.
.TP
.RB [ ECONNRESET ]
A connection was forcibly closed by a peer.
.TP
.RB [ EFAULT ]
The
.I message
or
.I dest_addr
parameter can not be accessed.
.TP
.RB [ EINTR ]
A signal interrupted
.BR sendto ()
before any data was transmitted.
.TP
.RB [ EMSGSIZE ]
The message is too large to be sent all at once, as the socket
requires.
.TP
.RB [ ENOTCONN ]
The socket is connection-mode but is not connected.
.TP
.RB [ ENOTSOCK ]
The
.I socket
argument does not refer to a socket.
.TP
.RB [ EOPNOTSUPP ]
The
.I socket
argument is associated with a socket that does not
support one or more of the values set in
.IR flags .
.TP
.RB [ EPIPE ]
The socket is shut down for writing, or the socket is
connection-mode and is no longer connected.  In the latter case,
and if the socket is of type
.BR SOCK_STREAM ,
the
.B SIGPIPE
signal is
generated to the calling process.
.PP
If the address family of the socket is
.BR AF_UNIX ,
then
.BR sendto ()
will
fail if:
.TP
.RB [ EIO ]
An I/O error occurred while reading from or writing to the file
system.
.TP
.RB [ ELOOP ]
Too many symbolic links were encountered in translating the
pathname in the socket address.
.TP
.RB [ ENAMETOOLONG ]
A component of a pathname exceeded
.RI { NAME_MAX }
characters, or an
entire pathname exceeded
.RI { PATH_MAX }
characters.
.TP
.RB [ ENOENT ]
A component of the pathname does not name an existing file or
the pathname is an empty string.
.TP
.RB [ ENOTDIR ]
A component of the path prefix of the pathname in the socket
address is not a directory.
.PP
The
.BR sendto ()
function may fail if:
.TP
.RB [ EACCES ]
Search permission is denied for a component of the path prefix;
or write access to the named socket is denied.
.TP
.RB [ EDESTADDRREQ ]
The socket is not connection-mode and does not have its peer
address set, and no destination address was specified.
.TP
.RB [ EHOSTUNREACH ]
The destination host cannot be reached (probably because the
host is down or a remote router cannot reach it).
.TP
.RB [ EINVAL ]
The
.I dest_len
argument is not a valid length for the address
family.
.TP
.RB [ EIO ]
An I/O error occurred while reading from or writing to the file
system.
.TP
.RB [ EISCONN ]
A destination address was specified and the socket is already
connected.  This error may or may not be returned for connection
mode sockets.
.TP
.RB [ ENETDOWN ]
The local interface used to reach the destination is down.
.TP
.RB [ ENETUNREACH ]
No route to the network is present.
.TP
.RB [ ENOBUFS ]
Insufficient resources were available in the system to perform
the operation.
.TP
.RB [ ENOMEM ]
Insufficient memory was available to fulfill the request.
.TP
.RB [ ENOSR ]
There were insufficient
.IR STREAMS (4)
resources available for the
operation to complete.
.PP
If the address family of the socket is
.BR AF_UNIX ,
then
.BR sendto ()
may
fail if:
.TP
.RB [ ENAMETOOLONG ]
Pathname resolution of a symbolic link produced an intermediate
result whose length exceeds
.RI { PATH_MAX }.
.SH "SEE ALSO"
.PP
.BR getsockopt (3),
.BR poll (2),
.BR recv (3),
.BR recvfrom (3),
.BR recvmsg (3),
.BR select (2),
.BR send (3),
.BR sendmsg (3),
.BR setsockopt (3),
.BR shutdown (3),
.BR socket (3),
.BR <sys/socket.h> (5).
.SH "CONFORMING TO"
.PP
The Open Group XNS Issue 5.2.
.[
xns
.]
.\"
.\"
.[
$LIST$
.]
.TI