Re: TCP/IP Sockets with GNAT.Sockets

[Eric Jacoboni <jaco@neottia.net>]

In article <42769099$0$24172$ba620e4c@news.skynet.be>, Adrien Plisson
<aplisson-news@stochastique.net> wrote:

> this is my Ada client:

Thanks, i'm gonna try to adapt it to my needs...

> =========================================================================
> with Ada.Text_IO,
>       GNAT.Sockets;
> procedure Main is
>      use GNAT.Sockets;
> 
>      Address  : Sock_Addr_Type := (Family_Inet, Inet_Addr( "127.0.0.1" 
> ), 5555);
>      Socket   : Socket_Type;
>      Channel  : Stream_Access;
> 
>      Data : String := "hello";
> 
> begin
>      Initialize;
>      Create_Socket( Socket );
>      Connect_Socket( Socket, Address );
>      Channel := Stream( Socket );
> 
>      String'Write( Channel, Data );
>      String'Read( Channel, Data );
>      Ada.Text_IO.Put_Line( Data );
> 
>      Close_Socket( Socket );
>      Finalize;
> end Main;

> as i already pointed to you on fr.comp.lang.ada, what you get from a 
> read is dependant on the PROTOCOL !

Well... Given the POP3 RFC:

"Responses in the POP3 consist of a status indicator and a keyword
   possibly followed by additional information.  All responses are
   terminated by a CRLF pair.  Responses may be up to 512 characters
   long, including the terminating CRLF.  "

So, i understand i have to read in a string and that's how i do with
every language i know. The pb with your exemple is that you have wrote
both the server and the client : you know the server will always send
fixed length strings, but that's not the case in real life. Sometimes
the POP3 server will send a "+OK", sometimes a "+OK 20 40", sometimes
another string. The protocol itself doesnt convey the length of the
answer and that's also true with other well known Internet protocols.
How to manage this with a Ada String ? I admit i don't see how to do.

> ultimately, you can 
> combine all the techniques to define powerful language-independant 
> protocols !

I don't want to define protocols, i just want be able to use an
existing protocol and to speak with a server that follow a well known
RFC.

-- 
jaco