SENDTO(3XNET)SENDTO(3XNET)NAMEsendto - send a message on a socket
SYNOPSIS
cc [ flag... ] file... -lxnet [ library ... ]
#include <sys/socket.h>
ssize_t sendto(int socket, const void *message, size_t length, int flags,
const struct sockaddr *dest_addr, socklen_t dest_len);
DESCRIPTION
The sendto() function sends a message through a connection-mode or con‐
nectionless-mode socket. If the socket is connectionless-mode, the
message will be sent to the address specified by dest_addr. If the
socket is connection-mode, dest_addr is ignored.
If the socket protocol supports broadcast and the specified address is
a broadcast address for the socket protocol, sendto() will fail if the
SO_BROADCAST option is not set for the socket.
The dest_addr argument specifies the address of the target. The length
argument specifies the length of the message.
Successful completion of a call to sendto() does not guarantee delivery
of the message. A return value of −1 indicates only locally-detected
errors.
If space is not available at the sending socket to hold the message to
be transmitted and the socket file descriptor does not have O_NONBLOCK
set, sendto() blocks until space is available. If space is not avail‐
able at the sending socket to hold the message to be transmitted and
the socket file descriptor does have O_NONBLOCK set, sendto() will
fail.
The socket in use may require the process to have appropriate privi‐
leges to use the sendto() function.
PARAMETERS
The function takes the following arguments:
socket
Specifies the socket file descriptor.
message
Points to a buffer containing the message to be sent.
length
Specifies the size of the message in bytes.
flags
Specifies the type of message transmission. Values of this
argument are formed by logically OR'ing zero or more of
the following flags:
MSG_EOR
Terminates a record (if supported by the proto‐
col)
MSG_OOB
Sends out-of-band data on sockets that support
out-of-band data. The significance and seman‐
tics of out-of-band data are protocol-specific.
dest_addr
Points to a sockaddr structure containing the destination
address. The length and format of the address depend on
the address family of the socket.
dest_len
Specifies the length of the sockaddr structure pointed to
by the dest_addr argument.
USAGE
The select(3C) and poll(2) functions can be used to determine when it
is possible to send more data.
RETURN VALUES
Upon successful completion, sendto() returns the number of bytes sent.
Otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
The sendto() function will fail if:
EAFNOSUPPORT
Addresses in the specified address family cannot be
used with this socket.
EAGAIN
EWOULDBLOCK
The socket's file descriptor is marked O_NONBLOCK and
the requested operation would block.
EBADF
The socket argument is not a valid file descriptor.
ECONNRESET
A connection was forcibly closed by a peer.
EFAULT
The message or destaddr parameter cannot be accessed.
EINTR
A signal interrupted sendto() before any data was
transmitted.
EMSGSIZE
The message is too large to be sent all at once, as the
socket requires.
ENOTCONN
The socket is connection-mode but is not connected.
ENOTSOCK
The socket argument does not refer to a socket.
EOPNOTSUPP
The socket argument is associated with a socket that
does not support one or more of the values set in
flags.
EPIPE
The socket is shut down for writing, or the socket is
connection-mode and is no longer connected. In the lat‐
ter case, and if the socket is of type SOCK_STREAM, the
SIGPIPE signal is generated to the calling thread.
If the address family of the socket is AF_UNIX, then sendto() will fail
if:
EIO
An I/O error occurred while reading from or writing to
the file system.
ELOOP
Too many symbolic links were encountered in translating
the pathname in the socket address.
ENAMETOOLONG
A component of a pathname exceeded NAME_MAX characters,
or an entire pathname exceeded PATH_MAX characters.
ENOENT
A component of the pathname does not name an existing
file or the pathname is an empty string.
ENOTDIR
A component of the path prefix of the pathname in the
socket address is not a directory.
The sendto() function may fail if:
EACCES
Search permission is denied for a component of the path
prefix; or write access to the named socket is denied.
EDESTADDRREQ
The socket is not connection-mode and does not have its
peer address set, and no destination address was speci‐
fied.
EHOSTUNREACH
The destination host cannot be reached (probably
because the host is down or a remote router cannot
reach it).
EINVAL
The dest_len argument is not a valid length for the
address family.
EIO
An I/O error occurred while reading from or writing to
the file system.
EISCONN
A destination address was specified and the socket is
already connected.
ENETDOWN
The local interface used to reach the destination is
down.
ENETUNREACH
No route to the network is present.
ENOBUFS
Insufficient resources were available in the system to
perform the operation.
ENOMEM
Insufficient memory was available to fulfill the
request.
ENOSR
There were insufficient STREAMS resources available for
the operation to complete.
If the address family of the socket is AF_UNIX, then sendto() may fail
if:
ENAMETOOLONG
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds PATH_MAX.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
├────────────────────┼─────────────────┤
│MT-Level │ MT-Safe │
└────────────────────┴─────────────────┘
SEE ALSOpoll(2), getsockopt(3XNET), recv(3XNET), recvfrom(3XNET),
recvmsg(3XNET), select(3C), send(3XNET), sendmsg(3XNET), setsock‐
opt(3XNET), shutdown(3XNET), socket(3XNET), attributes(5), standards(5)
Nov 1, 2003 SENDTO(3XNET)
