sendto - send a message on a socket
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);
The 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
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 available 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
privileges to use the sendto() function.
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 protocol)
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.
MSG_NOSIGNAL
Don't generate the SIGPIPE signal when a
stream-oriented socket is no longer connected.
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.
The select(3C) and poll(2) functions can be used to
determine when it is possible to send more data.
Upon successful completion, sendto() returns the number of
bytes sent. Otherwise, -1 is returned and errno is set to
indicate the error.
In addition to the errors documented below, an asynchronous error
generated by the underlying socket protocol may be returned. For the full
list of errors, please see the corresponding socket protocol manual page.
For example, for a list of TCP errors, please see tcp(4P).
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 latter case, and if the
socket is of type SOCK_STREAM, the SIGPIPE signal is generated
to the calling thread unless the MSG_NOSIGNAL flag is set.
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 specified.
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.
See attributes(7) for descriptions of the following
attributes:
| ATTRIBUTE
TYPE |
ATTRIBUTE VALUE |
| Interface Stability |
Standard |
| MT-Level |
MT-Safe |
poll(2), select(3C), sockaddr(3SOCKET),
getsockopt(3XNET), recv(3XNET), recvfrom(3XNET),
recvmsg(3XNET), send(3XNET), sendmsg(3XNET),
setsockopt(3XNET), shutdown(3XNET), socket(3XNET),
tcp(4P), attributes(7), standards(7)