send, sendto, sendmsg

Purpose

     Sends a message from a socket.

Library

     Sockets Library (libsock.a)

Syntax

     #include <sys/types.h>
     #include <sys/socket.h>

     int send (s, msg, len, flags)        int sendto (s, msg, len, flags, to, tolen)
     int s;                               int s;
     char *msg;                           char *msg;
     int len, flags;                      int len, flags;
                                          struct sockaddr *to;
     int sendmsg (s, msg, flags)          int tolen;
     int s;
     struct msghdr msg[ ];
     int flags;
     Description

     The send subroutine sends a  message only when the socket
     is in a connected state.   The sendto and sendmsg subrou-
     tines can be used at any time.

     Give the address  of the target by to,  with tolen speci-
     fying its size.   Specify the length of  the message with
     len.  If the  message is  too  long to  pass through  the
     underlying protocol,  the error EMSGSIZE is  returned and
     the message is not transmitted.

     No indication of failure to deliver is implied in a send.
     Return  values  of  -1  indicate  some  locally  detected
     errors.

     If  no space  for messages  is available  at the  sending
     socket to  hold the message  to be transmitted,  the send
     subroutine blocks unless the  socket is in a non-blocking
     I/O mode.

     Use the select  system call to determine when  it is pos-
     sible to send more data.

     The flags argument to send  a call is formed by logically
     OR-ing one or  both of the values shown  in the following
     list:

     MSG_OOB         Processes  out-of-band  data  on  sockets
                     that support SOCK_STREAM.

     MSG_DONTROUTE   Sends without using routing tables.

     For  a description  of the  msghdr structure,  see "recv,
     recvfrom, recvmsg."

     Return Value

     Upon successful completion, the number of characters sent
     is  returned.  If  the send,  sendto, or  sendmsg routine
     fails, a  value of -1  is returned,  and errno is  set to
     indicate the error.

     Diagnostics

     The subroutine fails if one  or more of the following are
     true:

     EBADF             The s parameter is not valid.

     ENOTSOCK          The s parameter refers to a file, not a
                       socket.

     EFAULT            The addr parameter is not in a writable
                       part of the user address space.

     EMSGSIZE          The socket requires that the message be
                       sent all  at once,  and the  message is
                       too large for that to happen.

     EWOULDBLOCK       The socket is  marked non-blocking, and
                       no  connections   are  present   to  be
                       accepted.

     Related Information

     In this book:  "recv, recvfrom, recvmsg" and "socket."