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<a name="echo-example"></a>
<div class="header">
<p>
Next: <a href="Other-examples.html#Other-examples" accesskey="n" rel="next">Other examples</a>, Up: <a href="Building-a-CORBA-application-with-PolyORB.html#Building-a-CORBA-application-with-PolyORB" accesskey="u" rel="up">Building a CORBA application with PolyORB</a> &nbsp; [<a href="About-This-Guide.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="echo-example-1"></a>
<h4 class="subsection">6.6.1 <code>echo</code> example</h4>


<p>We consider building a simple &ldquo;Echo&rdquo; CORBA server and client. This
application echoes a string. The source code for this example is
located in the <samp>examples/corba/echo</samp> directory in the PolyORB
distribution. This applications uses only basic elements of CORBA.
</p>
<p>To build this application, you need the following pieces of code:
</p>
<ol>
<li> IDL definition of an <code>echo</code> object
</li><li> Implementation code for the <code>echo</code> object
</li><li> Code for client and server nodes
</li></ol>

<a name="IDL-definition-of-an-echo-object"></a>
<h4 class="subsubsection">6.6.1.1 IDL definition of an <code>echo</code> object</h4>

<p>This interface defines an <code>echo</code> object with a unique method
<code>echoString</code>. Per construction, this method returns its argument.
</p>
<div class="smallexample">
<table class="cartouche" border="1"><tr><td>
<pre class="smallexample">
<b>interface</b> Echo {
  string echoString (<b>in</b> string Mesg);
};

</pre></td></tr></table>
</div>

<a name="Implementation-code-for-the-echo-object"></a>
<h4 class="subsubsection">6.6.1.2 Implementation code for the <code>echo</code> object</h4>

<p>Package <code>Echo.Impl</code> is an implementation of this interface. This
implementation follows the <em>IDL-to-Ada</em> mapping.
</p>
<div class="smallexample">
<pre class="smallexample">
------------------------------------------------------------------------------
--                                                                          --
--                           POLYORB COMPONENTS                             --
--                                                                          --
--                            E C H O . I M P L                             --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
--                                                                          --
-- This is free software;  you can redistribute it  and/or modify it  under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  This software is distributed in the hope  that it will be useful, --
-- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
-- License for  more details.                                               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- &lt;http://www.gnu.org/licenses/&gt;.                                          --
--                                                                          --
--                  PolyORB is maintained by AdaCore                        --
--                     (email: sales@adacore.com)                           --
--                                                                          --
------------------------------------------------------------------------------

<b>with</b> CORBA;
<b>with</b> PortableServer;

<b>package</b> Echo.Impl <b>is</b>

   --  My own implementation of echo object.
   --  This is simply used to define the operations.

   <b>type</b> Object <b>is</b> <b>new</b> PortableServer.Servant_Base <b>with</b> <b>null</b> <b>record</b>;

   <b>type</b> Object_Acc <b>is</b> <b>access</b> Object;

   <b>function</b> EchoString
     (Self : <b>access</b> Object;
      Mesg : CORBA.String)
     <b>return</b> CORBA.String;

<b>end</b> Echo.Impl;

</pre></div>
<div class="smallexample">
<pre class="smallexample">
------------------------------------------------------------------------------
--                                                                          --
--                           POLYORB COMPONENTS                             --
--                                                                          --
--                            E C H O . I M P L                             --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
--                                                                          --
-- This is free software;  you can redistribute it  and/or modify it  under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  This software is distributed in the hope  that it will be useful, --
-- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
-- License for  more details.                                               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- &lt;http://www.gnu.org/licenses/&gt;.                                          --
--                                                                          --
--                  PolyORB is maintained by AdaCore                        --
--                     (email: sales@adacore.com)                           --
--                                                                          --
------------------------------------------------------------------------------

<b>with</b> Ada.Text_IO;

<b>with</b> Echo.Skel;
<b>pragma</b> Warnings (Off, Echo.Skel);
--  No entity from Echo.Skel is referenced.

<b>package</b> <b>body</b> Echo.Impl <b>is</b>

   ----------------
   -- EchoString --
   ----------------

   <b>function</b> EchoString
     (Self : <b>access</b> Object;
      Mesg : CORBA.String)
     <b>return</b> CORBA.String
   <b>is</b>
      <b>pragma</b> Warnings (Off);
      <b>pragma</b> Unreferenced (Self);
      <b>pragma</b> Warnings (On);

      S : String := CORBA.To_Standard_String (Mesg);
      L : Natural := S'Last;
   <b>begin</b>
      <b>if</b> S'Length &gt; 13 <b>then</b>
         L := S'First + 12;
         S (L - 2 .. L) := (<b>others</b> =&gt; '.');
      <b>end</b> <b>if</b>;
      Ada.Text_IO.Put_Line
        (&quot;Echoing string: « &quot; &amp; S (S'First .. L) &amp; &quot; »&quot;);
      <b>return</b> Mesg;
   <b>end</b> EchoString;

<b>end</b> Echo.Impl;

</pre></div>

<p><i>Note: <code>Echo.Impl</code> body requires a dependency on
<code>Echo.Skel</code> to ensure the elaboration of skeleton code and the
correct setup of PolyORB&rsquo;s internals.</i>
</p>
<a name="Test-code-for-client-and-server-nodes"></a>
<h4 class="subsubsection">6.6.1.3 Test code for client and server nodes</h4>

<p>Client and server code demonstrate how to make a remote invocation on
a CORBA object, and how to set up an object on a server node.
</p>
<p><em>Note: the dependency on <code>PolyORB.Setup.Client</code> or
<code>PolyORB.Setup.No_Tasking_Server</code> enforces compile-time
configuration, see <a href="Sample-files.html#Sample-files">Sample files</a>.</em>
</p>
<ul>
<li> Client code tests a simple remote invocation on
an object. It is a no-tasking client. A reference to the object is built
from a stringified reference (or <code>IOR</code>), which is passed on command
line.

<div class="smallexample">
<pre class="smallexample">
------------------------------------------------------------------------------
--                                                                          --
--                           POLYORB COMPONENTS                             --
--                                                                          --
--                               C L I E N T                                --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
--                                                                          --
-- This is free software;  you can redistribute it  and/or modify it  under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  This software is distributed in the hope  that it will be useful, --
-- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
-- License for  more details.                                               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- &lt;http://www.gnu.org/licenses/&gt;.                                          --
--                                                                          --
--                  PolyORB is maintained by AdaCore                        --
--                     (email: sales@adacore.com)                           --
--                                                                          --
------------------------------------------------------------------------------

--  Echo client

<b>with</b> Ada.Command_Line;
<b>with</b> Ada.Text_IO;
<b>with</b> CORBA.ORB;

<b>with</b> Echo;

<b>with</b> PolyORB.Setup.Client;
<b>pragma</b> Warnings (Off, PolyORB.Setup.Client);

<b>with</b> PolyORB.Utils.Report;

<b>procedure</b> Client <b>is</b>
   <b>use</b> Ada.Command_Line;
   <b>use</b> Ada.Text_IO;
   <b>use</b> PolyORB.Utils.Report;
   <b>use</b> <b>type</b> CORBA.String;

   Sent_Msg, Rcvd_Msg : CORBA.String;
   myecho : Echo.Ref;

   Length : Natural := 0;
   Calls  : Natural := 1;
<b>begin</b>
   New_Test (&quot;Echo client&quot;);

   CORBA.ORB.Initialize (&quot;ORB&quot;);
   <b>if</b> Argument_Count <b>not</b> <b>in</b> 1 .. 3 <b>then</b>
      Put_Line
        (&quot;usage: client &lt;IOR_string_from_server&gt;|-i [strlen [num <b>of</b> calls]]&quot;);
      <b>return</b>;
   <b>end</b> <b>if</b>;

   --  Getting the CORBA.Object

   CORBA.ORB.String_To_Object
     (CORBA.To_CORBA_String (Ada.Command_Line.Argument (1)), myecho);

   --  Get optional arguments Length and Calls

   <b>if</b> Argument_Count &gt;= 2 <b>then</b>
      Length := Natural'Value (Ada.Command_Line.Argument (2));
   <b>end</b> <b>if</b>;

   <b>if</b> Argument_Count &gt;= 3 <b>then</b>
      Calls := Natural'Value (Ada.Command_Line.Argument (3));
   <b>end</b> <b>if</b>;

   --  Checking if it worked

   <b>if</b> Echo.Is_Nil (myecho) <b>then</b>
      Put_Line (&quot;main : cannot <b>in</b>voke on a nil reference&quot;);
      <b>return</b>;
   <b>end</b> <b>if</b>;

   --  Sending message

   <b>if</b> Length = 0 <b>then</b>
      Sent_Msg := CORBA.To_CORBA_String (Standard.String'(&quot;Hello Ada !&quot;));
   <b>else</b>
      Sent_Msg := CORBA.To_CORBA_String
                    (Standard.String'(1 .. Length =&gt; 'X'));
   <b>end</b> <b>if</b>;

   <b>for</b> J <b>in</b> 1 .. Calls <b>loop</b>
      Rcvd_Msg := Echo.echoString (myecho, Sent_Msg);
   <b>end</b> <b>loop</b>;

   <b>if</b> Rcvd_Msg /= Sent_Msg <b>then</b>
      <b>raise</b> Program_Error <b>with</b> &quot;<b>in</b>correct string <b>return</b>ed by server&quot;;
   <b>end</b> <b>if</b>;

   --  Printing result

   <b>if</b> Length = 0 <b>then</b>
      Put_Line (&quot;I said : &quot; &amp; CORBA.To_Standard_String (Sent_Msg));
      Put_Line
        (&quot;The object answered : &quot; &amp; CORBA.To_Standard_String (Rcvd_Msg));

   <b>else</b>
      Put_Line (&quot;I said : 'X' *&quot; &amp; Length'Img);
      Put_Line (&quot;The object answered the same.&quot;);
   <b>end</b> <b>if</b>;

   End_Report;

<b>exception</b>
   <b>when</b> E : CORBA.Transient =&gt;
      Output (&quot;echo test&quot;, False);
      <b>declare</b>
         Memb : CORBA.System_Exception_Members;
      <b>begin</b>
         CORBA.Get_Members (E, Memb);
         Put (&quot;received <b>exception</b> transient, minor&quot;);
         Put (CORBA.Unsigned_Long'Image (Memb.Minor));
         Put (&quot;, completion status: &quot;);
         Put_Line (CORBA.Completion_Status'Image (Memb.Completed));

         End_Report;
      <b>end</b>;
<b>end</b> Client;

</pre></div>

</li><li> The server code sets up a no-tasking node. The object is registered to
the <code>RootPOA</code>. Then an <code>IOR</code> reference is built to enable
interaction with other nodes.

<div class="smallexample">
<pre class="smallexample">
------------------------------------------------------------------------------
--                                                                          --
--                           POLYORB COMPONENTS                             --
--                                                                          --
--                               S E R V E R                                --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
--                                                                          --
-- This is free software;  you can redistribute it  and/or modify it  under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  This software is distributed in the hope  that it will be useful, --
-- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
-- License for  more details.                                               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- &lt;http://www.gnu.org/licenses/&gt;.                                          --
--                                                                          --
--                  PolyORB is maintained by AdaCore                        --
--                     (email: sales@adacore.com)                           --
--                                                                          --
------------------------------------------------------------------------------

<b>with</b> Ada.Exceptions;
<b>with</b> Ada.Text_IO; <b>use</b> Ada.Text_IO;

<b>with</b> CORBA.Impl;
<b>with</b> CORBA.Object;
<b>with</b> CORBA.ORB;

<b>with</b> PortableServer.POA.Helper;
<b>with</b> PortableServer.POAManager;

<b>with</b> Echo.Impl;

<b>with</b> PolyORB.CORBA_P.CORBALOC;

--  Setup server node: use no tasking default configuration

<b>with</b> PolyORB.Setup.No_Tasking_Server;
<b>pragma</b> Warnings (Off, PolyORB.Setup.No_Tasking_Server);

<b>procedure</b> Server <b>is</b>
<b>begin</b>

   <b>declare</b>
      Argv : CORBA.ORB.Arg_List := CORBA.ORB.Command_Line_Arguments;

   <b>begin</b>
      CORBA.ORB.Init (CORBA.ORB.To_CORBA_String (&quot;ORB&quot;), Argv);

      <b>declare</b>
         Root_POA : PortableServer.POA.Local_Ref;

         Ref : CORBA.Object.Ref;

         Obj : <b>constant</b> CORBA.Impl.Object_Ptr := <b>new</b> Echo.Impl.Object;

      <b>begin</b>

         --  Retrieve Root POA

         Root_POA := PortableServer.POA.Helper.To_Local_Ref
           (CORBA.ORB.Resolve_Initial_References
            (CORBA.ORB.To_CORBA_String (&quot;RootPOA&quot;)));

         PortableServer.POAManager.Activate
           (PortableServer.POA.Get_The_POAManager (Root_POA));

         --  Set up new object

         Ref := PortableServer.POA.Servant_To_Reference
           (Root_POA, PortableServer.Servant (Obj));

         --  Output IOR

         Put_Line
           (&quot;'&quot;
            &amp; CORBA.To_Standard_String (CORBA.Object.Object_To_String (Ref))
            &amp; &quot;'&quot;);
         New_Line;

         --  Output corbaloc

         Put_Line
           (&quot;'&quot;
            &amp; CORBA.To_Standard_String
            (PolyORB.CORBA_P.CORBALOC.Object_To_Corbaloc (Ref))
            &amp; &quot;'&quot;);

         --  Launch the server. CORBA.ORB.Run is supposed to never return,
         --  print a message if it does.

         CORBA.ORB.Run;

         Put_Line (&quot;ORB main <b>loop</b> <b>terminate</b>d!&quot;);
      <b>end</b>;
   <b>end</b>;
<b>exception</b>
   <b>when</b> E : <b>others</b> =&gt;
      Put_Line
        (&quot;Echo server <b>raise</b>d &quot; &amp; Ada.Exceptions.Exception_Information (E));
      <b>raise</b>;
<b>end</b> Server;

</pre></div>

</li></ul>

<a name="Compilation-and-execution"></a>
<h4 class="subsubsection">6.6.1.4 Compilation and execution</h4>

<p>To compile this demo,
</p><ol>
<li> Process the IDL file with <code>idlac</code> (or <code>iac</code>)
<div class="smallexample">
<pre class="smallexample"> $ idlac echo.idl
</pre></div>

</li><li> Compile the client node
<div class="smallexample">
<pre class="smallexample"> $ gnatmake client.adb `polyorb-config`
</pre></div>

</li><li> Compile the server node
<div class="smallexample">
<pre class="smallexample"> $ gnatmake server.adb `polyorb-config`
</pre></div>

</li></ol>

<p>Note the use of backticks (&lsquo;). This means that
<code>polyorb-config</code> is first executed, and then the command line
is replaced with the output of the script, setting up library and
include paths and library names.
</p>
<p>To run this demo:
</p>
<ul>
<li> run <samp>server</samp>, the server outputs its IOR, a hexadecimal
string with the IOR: prefix:
<div class="smallexample">
<pre class="smallexample">$ ./server
Loading configuration from polyorb.conf
No polyorb.conf configuration file.
'IOR:01534f410d00000049444c3[..]'
</pre></div>

</li><li> In another shell, run <samp>client</samp>, passing cut-and-pasting the
complete IOR on the command line:
<div class="smallexample">
<pre class="smallexample">$ ./client 'IOR:01534f410d00000049444c3[..]'
Echoing string: &quot; Hello Ada ! &quot;
I said : Hello Ada !
The object answered : Hello Ada !
</pre></div>
</li></ul>

<hr>
<div class="header">
<p>
Next: <a href="Other-examples.html#Other-examples" accesskey="n" rel="next">Other examples</a>, Up: <a href="Building-a-CORBA-application-with-PolyORB.html#Building-a-CORBA-application-with-PolyORB" accesskey="u" rel="up">Building a CORBA application with PolyORB</a> &nbsp; [<a href="About-This-Guide.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
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