>String'Output (Channel,"����getstatus");
  In the definition of 'Output, ARM 13.13.2(21) says
"S'Output writes the value of Item to Stream, including any bounds or
discriminants."  So you are probably sending 4 bytes containing the
integer 1 (the lower bound of the string you are sending), then the
integer 13 (the upper bound), followed the 13 bytes you think you are
sending.  Similarly 'Input expects to read the bounds, then the
data.  Using 'Write instead of 'Output will probably solve the sending
problem, but S'Read is a procedure, not a function, since YOU will have
to supply the bounds, which presumably you can get from the recv (or
whatever gnat.sockets uses for datagram input).