Re: GNAT.sockets UDP Example

[Simon Wright <simon@pushface.org>]

lemchens@lemmies.lb.bawue.de (arvids lemchens) writes:

> If i try to compile it:
> 
> -----
> ich@pc3:/transfer/ich2/ada/my/myrdate$ gnatmake -gnatf sendudp.adb
> gnatgcc -c -gnatf sendudp.adb
> sendudp.adb:10:11: warning: file name does not match unit name, should be "myrdate.adb"
> sendudp.adb:27:05: no candidate interpretations match the actuals:
> sendudp.adb:27:05: missing argument for parameter "To" in call to "send_socket" declared at g-socket.ads:653
> sendudp.adb:27:35: expected type "Ada.Streams.Stream_Element_Offset"

I don't know what you think this means -- if you look at the spec of
Send_Socket it says

   procedure Send_Socket
     (Socket : Socket_Type;
      Item   : Ada.Streams.Stream_Element_Array;
      Last   : out Ada.Streams.Stream_Element_Offset);
   --  Transmit a message to another socket. Note that Last is set to
   --  Item'First when socket has been closed by peer. This is not an
   --  error and no exception is raised. Raise Socket_Error on error;

Last is an *out* parameter, which means you need to supply an actual
variable of the correct type.

       Kahnung  : Ada.Streams.Stream_Element_Array := (1, 2, 3);
       Last : Ada.Streams.Stream_Element_Offset;

   begin
       Initialize (Process_Blocking_IO => False);
       Address.Addr := Addresses (Get_Host_By_Name(Argument(1)), 1);
       Address.Port := 37;
       Create_Socket (Socket, Family_Inet, Socket_Datagram);
       --  Rest from TCP
       --    Connect_Socket (Socket, Address);
       --    Channel := Stream (Socket);
       Send_Socket (Socket, Kahnung, Last);

> sendudp.adb:27:35: found type "Ada.Streams.Stream_Element"
> sendudp.adb:27:35:   ==> in call to "Send_Socket" at g-socket.ads:645
> gnatmake: "sendudp.adb" compilation error

When I correct this error I get (GCC-3.2, compiling with -bargs -E):

   smaug.pushface.org[15]$ ./myrdate myrouter

   Execution terminated by unhandled exception
   Exception name: GNAT.SOCKETS.SOCKET_ERROR
   Message: [107] Transport endpoint is not connected
   Call stack traceback locations:
   0x8062e3d 0x806350d 0x804a6d3 0x804a4f2 0x4003d27e

and I suspect maybe you need to call Bind_Socket??? -- hmm, now I get

   smaug.pushface.org[16]$ ./myrdate myrouter

   Execution terminated by unhandled exception
   Exception name: GNAT.SOCKETS.SOCKET_ERROR
   Message: [13] Permission denied

whereas

   Send_Socket (Socket, Kahnung, Last, Address);

ends up with a constraint error. Oh well, I guess I need to get GDB
working now ...