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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.