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NAME
sendto - send a message from a socket
SYNOPSIS
#include <network.h>
int sendto(int s, const void *msg, int len, unsigned int
flags, const struct sockaddr *to, int tolen);
DESCRIPTION
Sendto is used to transmit a message
to another socket.
The address of the target is given by to with tolen speci
fying its size. The length of the message is given by
len. If the message is too long to pass atomically
through the underlying protocol, the error EMSGSIZE is
returned, and the message is not transmitted.
No indication of failure to deliver is implicit in a send.
Locally detected errors are indicated by a return value of
-1.
When the message does not fit into the send buffer of the
socket, send normally blocks, unless the socket has been
placed in non-blocking I/O mode. In non-blocking mode it
would return EAGAIN in this case. The select(2) call may
be used to determine when it is possible to send more
data.
The flags parameter may include one or more of the follow
ing:
#define MSG_OOB 0x1 /* process out-of-band data */
#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
#define MSG_DONTWAIT 0x40 /* don't block */
#define MSG_NOSIGNAL 0x2000 /* don't raise SIGPIPE */
MSG_OOB
Sends out-of-band data on sockets that support this
notion (e.g. SOCK_STREAM); the underlying protocol
must also support out-of-band data.
MSG_DONTROUTE
Bypasses the usual routing table lookup and sends
the packet directly to the interface described by
the destination address. This is usually used only
by diagnostic or routing programs.
MSG_DONTWAIT
Enables non-blocking operation; if the operation
would block, EAGAIN is returned.
MSG_NOSIGNAL
Requests not to send SIGPIPE on errors on stream
oriented sockets when the other end breaks the con
nection. The EPIPE error is still returned.
See recv(2) for a description of the msghdr structure. You
may send control information using the msg_control and
msg_controllen members. The maximum control buffer length
the kernel can process is limited by the net.core.opt
mem_max sysctl; see socket(4).
RETURN VALUES
The calls return the number of characters sent, or -1 if
an error occurred.
ERRORS
These are some standard errors generated by the socket
layer. Additional errors may be generated and returned
from the underlying protocol modules; see their respective
manual pages.
EBADF An invalid descriptor was specified.
ENOTSOCK
The argument s is not a socket.
EMSGSIZE
The socket requires that message be sent atomi
cally, and the size of the message to be sent made
this impossible.
EAGAIN The socket is marked non-blocking and the
requested operation would block.
ENOBUFS The system was unable to allocate an internal mem
ory block. The operation may succeed when buffers
become available.
EINTR A signal occurred.
ENOMEM No memory available.
EINVAL Invalid argument passed.
EPIPE The local end has been shut down on a connection
oriented socket. In this case the process will
also receive a SIGPIPE unless MSG_NOSIGNAL is set.
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