Re: Sockets Example Sought

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Fri, 23 Nov 2012 15:58:53 -0600, Robert Love wrote:

> On 2012-11-23 18:32:52 +0000, Simon Wright said:
> 
>> Robert Love <rblove@airmail.net> writes:
>> 
>>> Does anyone have an example of a multi-client server in Ada they care
>>> to share?  It should use the Gnat.Sockets package.  I've seen samples
>>> but they don't seem complete, or at least my understanding isn't
>>> complete<grin>.
>>> 
>>> Thanks in advance.
>> 
>> task body Server in http://goo.gl/bXVw7 ? (lines 59 .. 143)
> 
> What happens at line 120, the else clause on if Server = Socket_Server? 
>  Is that where data is read in on the socket?

Socket-select might be a bit difficult to start with. Unless you expect
hundreds of simultaneous connections, there is a much simpler pattern that
uses 1-2 tasks (half- or full-duplex I/O) per connection with so-called
blocking sockets:

   Client : Sock_Addr_Type;
   Server : Sock_Addr_Type;
   Socket : Socket_Type;
   Data   : Socket_Type;
begin
   Server.Addr := ...;
   Server.Port := ...;
   Create_Socket (Socket);
   Bind_Socket (Socket, Server);
   Listen_Socket (Socket);
   loop
      Accept_Socket (Socket, Data, Client);
      -- Start an I/O task, give it Data to communicate over.
      -- Client holds the address of the client. The task will
      -- dispose the socket Data calling Shutdown_Socket and
      -- then Close_Socket on it, when communication is over
   end loop;

> I assume the client opens the socket and the server detects it, then at 
> various times the client makes data requests by sending string data.

That happens later on when the client connects its socket. A client does:

   Create_Socket
   Bind_Socket       -- Client address
   Connect_Socket -- Server address
      -- I/O
   Shutdown_Socket
   Close_Socket

The server listening to a socket gets a new socket when its calls to
Accept_Socket. Accept waits for a client to come. This happens per each
connection, i.e. for each client connection there is one accept completed
on the server side. After accept returned a socket, this socket and the
client's socket are connected, so that when one side writes something into
its socket another side reads that from the socket of its own.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de