sendmsg(3XNET) X/Open Networking Services Library Functions sendmsg(3XNET)NAMEsendmsg - send a message on a socket using a message structure
SYNOPSIS
cc [ flag ... ] file ... -lxnet [ library ... ]
#include <sys/socket.h>
ssize_t sendmsg(int socket, const struct msghdr *message, int flags);
PARAMETERS
The function takes the following arguments:
socket Specifies the socket file descriptor.
message Points to a msghdr structure, containing both the des‐
tination address and the buffers for the outgoing mes‐
sage. The length and format of the address depend on
the address family of the socket. The msg_flags member
is ignored.
flags Specifies the type of message transmission. The appli‐
cation may specify 0 or the following flag:
MSG_EOR Terminates a record (if sup‐
ported by the protocol)
MSG_OOB Sends out-of-band data on sock‐
ets that support out-of-bound
data. The significance and
semantics of out-of-band data
are protocol-specific.
DESCRIPTION
The sendmsg() 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 msghdr. If the socket
is connection-mode, the destination address in msghdr is ignored.
The msg_iov and msg_iovlen fields of message specify zero or more
buffers containing the data to be sent. msg_iov points to an array of
iovec structures; msg_iovlen must be set to the dimension of this
array. In each iovec structure, the iov_base field specifies a stor‐
age area and the iov_len field gives its size in bytes. Some of these
sizes can be zero. The data from each storage area indicated by
msg_iov is sent in turn.
Successful completion of a call to sendmsg() does not guarantee deliv‐
ery 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, sendmsg() function blocks until space is available. If space is
not available at the sending socket to hold the message to be transmit‐
ted and the socket file descriptor does have O_NONBLOCK set, sendmsg()
function will fail.
If the socket protocol supports broadcast and the specified address is
a broadcast address for the socket protocol, sendmsg() will fail if the
SO_BROADCAST option is not set for the socket.
The socket in use may require the process to have appropriate privi‐
leges to use the sendmsg() function.
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, sendmsg() function returns the number of
bytes sent. Otherwise, −1 is returned and errno is set to indicate the
error.
ERRORS
The sendmsg() function will fail if:
EAGAIN The socket's file descriptor is marked O_NON‐
EWOULDBLOCK BLOCK and the requested operation would block.
EAFNOSUPPORT Addresses in the specified address family can‐
not be used with this socket.
EBADF The socket argument is not a valid file
descriptor.
ECONNRESET A connection was forcibly closed by a peer.
EFAULT The message parameter, or storage pointed to
by the msg_name, msg_control or msg_iov
fields of the message parameter, or storage
pointed to by the iovec structures pointed to
by the msg_iov field can not be accessed.
EINTR A signal interrupted sendmsg() before any data
was transmitted.
EINVAL The sum of the iov_len values overflows an
ssize_t.
EMSGSIZE The message is to large to be sent all at once
(as the socket requires), or the msg_iovlen
member of the msghdr structure pointed to by
message is less than or equal to 0 or is
greater than IOV_MAX.
ENOTCONN The socket is connection-mode but is not con‐
nected.
ENOTSOCK The socket argument does not refer 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 con‐
nected. In the latter 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 sendmsg() 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 sendmsg() 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 specified.
EHOSTUNREACH The destination host cannot be reached (proba‐
bly because the host is down or a remote router
cannot reach it).
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 destina‐
tion 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 sendmsg() 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), sendto(3XNET), setsock‐
opt(3XNET), shutdown(3XNET), socket(3XNET), attributes(5), standards(5)SunOS 5.10 1 Nov 2003 sendmsg(3XNET)
