How to Create an UDP client in Ada - sockets

Question

I'm working on UDP communications using Ada. This code has to send some data to another host which is going to process it. I'm trying to send an initial message to start the communication, but it doesn't work. My client code is the following:
with GNAT.Sockets;
use GNAT.Sockets;
with Ada.Text_IO;
with Ada.Exceptions;
use Ada.Exceptions;
procedure Client_Send is
task Send is
entry Start;
entry Stop;
end Send;
task body Send is
Address : Sock_Addr_Type;
Socket : Socket_Type;
Channel : Stream_Access;
begin
accept Start;
-- See comments in Ping section for the first steps.
Address.Addr := Inet_Addr( "192.168.0.1" );
Address.Port := 7777;
Create_Socket (Socket,Family_Inet,Socket_Datagram);
Bind_Socket (Socket, Address);
Channel := Stream (Socket);
String'Output (Channel, "Hello world");
Free(Channel);
Ada.Text_IO.Put_Line ("Mesnaje Enviado");
Close_Socket (Socket);
accept Stop;
exception when E : others =>
Ada.Text_IO.Put_Line
(Exception_Name (E) & ": " & Exception_Message (E));
end Send;
begin
Initialize (Process_Blocking_IO => False);
Send.Start;
Send.Stop;
Finalize;
end Client_Send;
I'm using Wireshark to view the inbound traffic, but it doesn't receive anything.

Answer 1

Here is a simple UDP Client / Server in Ada with GNAT Sockets :
Client:
with Ada.Streams;
with Ada.Text_IO;
with GNAT.Sockets;
procedure UDP_Client is
use GNAT.Sockets;
Address : Sock_Addr_Type;
Socket : Socket_Type;
Data : constant Ada.Streams.Stream_Element_Array (1 .. 512) := (others => 42);
Last : Ada.Streams.Stream_Element_Offset;
begin
Address.Port := 50001;
Address.Addr := Inet_Addr ("127.0.0.1");
Create_Socket (Socket, Family_Inet, Socket_Datagram);
Send_Socket (Socket, Data, Last, Address);
Ada.Text_IO.Put_Line ("last :" & Last'Img);
end UDP_Client;
Server :
with Ada.Streams;
with Ada.Text_IO;
with GNAT.Sockets;
procedure UDP_Server is
use GNAT.Sockets;
Server : Socket_Type;
Address, From : Sock_Addr_Type;
Data : Ada.Streams.Stream_Element_Array (1 .. 512);
Last : Ada.Streams.Stream_Element_Offset;
Watchdog : Natural := 0;
begin
Create_Socket (Server, Family_Inet, Socket_Datagram);
Set_Socket_Option
(Server,
Socket_Level,
(Reuse_Address, True));
Set_Socket_Option
(Server,
Socket_Level,
(Receive_Timeout,
Timeout => 1.0));
Address.Addr := Any_Inet_Addr;
Address.Port := 50001;
Bind_Socket (Server, Address);
loop
begin
GNAT.Sockets.Receive_Socket (Server, Data, Last, From);
Ada.Text_IO.Put_Line ("last : " & Last'Img);
Ada.Text_IO.Put_Line ("from : " & Image (From.Addr));
exception
when Socket_Error =>
Watchdog := Watchdog + 1;
exit when Watchdog = 10;
end;
end loop;
end UDP_Server;

Answer 2

There are (at least) two problems with your program:
You are mixing up UDP and TCP. UDP is not a stream-oriented
protocol, so you shouldn't treat it as an Ada stream.
You aren't setting up a connection with another machine.
Here is an example of a program communicating over UDP: https://bitbucket.org/sparre/udp-chat