Sends gathered bytes through a socket to any other socket.
    Format
      #include  <types.h>
      #include  <socket.h>
      int sendmsg  ( int s, struct msghdr *msg, int flags ); (BSD
                   Version 4.4)
      int sendmsg  ( int s, struct omsghdr *msg, int flags ); (BSD
                   Version 4.3)