Re: Question about Streams and UDP sockets using GNAT.Sockets

[Simon Wright <simon@pushface.org>]

"lekktu@gmail.com" <lekktu@gmail.com> writes:

> I'm trying to broadcast an UDP packet, with the following test code:

> The trouble I'm having is not about sockets, but the streams vs.
> sockets interaction. The above code does not send one UDP packet,
> but four, one for each byte of the test message. What I'm doing
> wrong?

If you tried to read the data you would probably not have noticed
anything wrong; because GNAT (GNAT.Sockets, anyway) is rather naive
about UDP sockets. It would have happily done 4 reads, one for each
byte of the test message.

The only way I can see to get UDP working is

(1) stream the record to be output to a memory stream,then write the
    bytes of the stream to the socket stream in one go;

(2) read a datagram into a maximally-sized Stream Element Array (1600
    bytes or so?), populate a memory stream with the bytes actually
    read, read the record to be input from that.

Personally I think that letting us get a Stream for a GNAT.Sockets
datagram socket is almost bound to result in error and shouldn't be
allowed, I couldn't persuade AdaCore of that!