Sockets Library Functions send(3SOCKET)
NAME
send, sendto, sendmsg - send a message from a socket
SYNOPSIS
cc [ flag... ] file... -lsocket -lnsl [ library... ]
#include
#include
ssizet send(int s, const void *msg, sizet len, int flags);
ssizet sendto(int s, const void *msg, sizet len, int flags,
const struct sockaddr *to, int tolen);
ssizet 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 mes-
sage is supplied by the len parameter. For socket types such
as SOCKDGRAM and SOCKRAW that require atomic messages, the
error EMSGSIZE is returned and the message is not transmit-
ted when it is too long to pass atomically through the
underlying protocol. The same restrictions do not apply to
SOCKSTREAM 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:
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Sockets Library Functions send(3SOCKET)
MSGOB Send out-of-band data on sockets that sup-
port this notion. The underlying protocol
must also support out-of-band data. Only
SOCKSTREAM sockets created in the AFINET
or the AFINET6 address family support
out-of-band data.
MSGDONTROUTE The SODONTROUTE 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.
ERORS
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 operation.
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
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Sockets Library Functions send(3SOCKET)
suitable buffer. In such a case, the opera-
tion can be retried later.
ECONREFUSED 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 Unreach-
able 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 ssizet.
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 family.
EISCON A destination address was specified and the socket
is already connected.
The sendmsg() function returns errors under the following
conditions:
EINVAL The msgiovlen member of the msghdr structure
pointed to by msg is less than or equal to 0, or
the sum of the iovlen values in the msgiov array
overflows a ssizet.
EINVAL One of the iovlen values in the msgiov array
member of the msghdr structure pointed to by msg
is negative, or the sum of the iovlen values in
the msgiov array overflows a ssizet.
The send() function returns errors under the following con-
ditions:
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Sockets Library Functions send(3SOCKET)
EPIPE The socket is shut down for writing, or the socket
is connection-mode and is no longer connected. In
the latter case, if the socket is of type
SOCKSTREAM, the SIGPIPE signal is generated to the
calling thread.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability Stable
MT-Level Safe
SEE ALSO
fcntl(2), poll(2), write(2), connect(3SOCKET),
getsockopt(3SOCKET), recv(3SOCKET), select(3C),
socket(3SOCKET), socket.h(3HEAD), attributes(5)
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