send(3SOCKET) Sockets Library Functions send(3SOCKET)NAME
send, sendto, sendmsg - send a message from a socket
SYNOPSIS
cc [ flag... ] file... -lsocket -lnsl [ library... ]
#include <sys/types.h>
#include <sys/socket.h>
ssize_t send(int s, const void *msg, size_t len, int flags);
ssize_t sendto(int s, const void *msg, size_t len, int flags, const
struct sockaddr *to, int tolen);
ssize_t sendmsg(int s, const struct msghdr *msg, int flags);
DESCRIPTION
The send(), sendto(), and sendmsg() functions are used to transmit a
message to another transport end-point. The send() function can be used
only when the socket is in a connected state. See connect(3SOCKET).
The sendto() and sendmsg() functions can be used at any time. The s
socket is created with socket(3SOCKET).
The address of the target is supplied by to with a tolen parameter used
to specify the size. The length of the message is supplied by the len
parameter. For socket types such as SOCK_DGRAM and SOCK_RAW that
require atomic messages, the error EMSGSIZE is returned and the message
is not transmitted when it is too long to pass atomically through the
underlying protocol. The same restrictions do not apply to SOCK_STREAM
sockets.
A return value −1 indicates locally detected errors. It does not imply
a delivery failure.
If the socket does not have enough buffer space available to hold a
message, the send() function blocks the message, unless the socket has
been placed in non-blocking I/O mode (see fcntl(2)). The select(3C) or
poll(2) call can be used to determine when it is possible to send more
data.
The flags parameter is formed from the bitwise OR of zero or more of
the following:
MSG_OOB Send out-of-band data on sockets that support
this notion. The underlying protocol must also
support out-of-band data. Only SOCK_STREAM
sockets created in the AF_INET or the AF_INET6
address family support out-of-band data.
MSG_DONTROUTE The SO_DONTROUTE option is turned on for the
duration of the operation. It is used only by
diagnostic or routing programs.
See recv(3SOCKET) for a description of the msghdr structure.
RETURN VALUES
Upon successful completion, these functions return the number of bytes
sent. Otherwise, they return -1 and set errno to indicate the error.
ERRORS
The send(), sendto(), and sendmsg() functions return errors under the
following conditions:
EBADF s is not a valid file descriptor.
EINTR The operation was interrupted by delivery of a signal
before any data could be buffered to be sent.
EMSGSIZE The socket requires that the message be sent atomically
and the message is too long.
ENOMEM Insufficient memory is available to complete the opera‐
tion.
ENOSR Insufficient STREAMS resources are available for the
operation to complete.
ENOTSOCK s is not a socket.
EWOULDBLOCK The socket is marked non-blocking and the requested
operation would block. EWOULDBLOCK is also returned
when sufficient memory is not immediately available to
allocate a suitable buffer. In such a case, the opera‐
tion can be retried later.
ECONNREFUSED The requested connection was refused by the peer. For
conected IPv4 and IPv6 datagram sockets, this indicates
that the system received an ICMP Destination Port
Unreachable message from the peer in response to some
prior transmission.
The send() and sendto() functions return errors under the following
conditions:
EINVAL The len argument overflows a ssize_t.
The sendto() function returns errors under the following conditions:
EINVAL The value specified for the tolen parameter is not the
size of a valid address for the specified address fam‐
ily.
EISCON A destination address was specified and the socket is
already connected.
The sendmsg() function returns errors under the following conditions:
EINVAL The msg_iovlen member of the msghdr structure pointed
to by msg is less than or equal to 0, or the sum of the
iov_len values in the msg_iov array overflows a
ssize_t.
EINVAL One of the iov_len values in the msg_iov array member
of the msghdr structure pointed to by msg is negative,
or the sum of the iov_len values in the msg_iov array
overflows a ssize_t.
The send() function returns errors under the following conditions:
EPIPE The socket is shut down for writing, or the socket is
connection-mode and is no longer connected. In the lat‐
ter case, if the socket is of type SOCK_STREAM, the
SIGPIPE signal is generated to the calling thread.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Stable │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOfcntl(2), poll(2), write(2), connect(3SOCKET), getsockopt(3SOCKET),
recv(3SOCKET), select(3C), socket(3SOCKET), socket.h(3HEAD),
attributes(5)SunOS 5.10 16 Jul 2004 send(3SOCKET)
