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