Lua subscriber to C++ api Publishers

Hello Kenny,

Yes: it is possible to publish in C++ and subscribe in Lua! With RTI Connext DDS you can pick many languages (C/C++/Java/Ada/Lua/C#) and all your application will communicate with each other seamlessly!!

Let’s go to your specific example. It is very easy and you did almost all the steps:

Publisher in C++:

• take your idl and with rtiddsgen generate a c++ example:

rtiddsgen -example x64Darwin12clang4.1 test.idl

• modify your test_publisher.cxx

/* Main loop */
for (count=0; (sample_count == 0) || (count < sample_count); ++count) {
    printf("Writing MyModule_PhoneCall2, count %d\n", count);
    /* Modify the data to be sent here */

    instance -&gt;Member1[1][1] = count; /This is what you want to add */

    retcode = MyModule_PhoneCall2_writer->write(*instance, instance_handle);
    if (retcode != DDS_RETCODE_OK) {
        printf("write error %d\n", retcode);
    }
    NDDSUtility::sleep(send_period);
}

• then compile your example:

gmake -f makefile_test_x64Darwin12clang4.1

Let's now move to the subscriber in Lua:

• You can generate the xml type description from the idl using rtiddsgen:

 rtiddsgen -convertToXml test.idl

a test.xml file is created that contains your type definition.

• Now you have to define in xml your domain/subscribe/topic and reader. For the type you can use the content of the xml we just generated. This is the complete file: quite simple but let me know if you have any question about it. 

• Now the simple Lua code to read your type:

if not reader then
  reader = CONTAINER.READER["MySubscriber::MyReader"]
  if reader == nil then print("Error: reader is nil") end
end

reader:take()

for  i, sample in ipairs(reader.samples) do
  if (not reader.infos[i].valid_data) then
    print("\t invalid data!")
  else
    print("\t Member1[2][2]=", sample['Member1[2][2]']) --note in Lua indexes start from 1 so if in C++ you are publishing Member1[1][1], in lua you have to read Member1[2][2]
  end
end

Now, run!!!

• In one terminal run your C++ publisher 

$ ./objs/x64Darwin12clang4.1/test_publisher
Writing MyModule_PhoneCall2, count 0
Writing MyModule_PhoneCall2, count 1
Writing MyModule_PhoneCall2, count 2
Writing MyModule_PhoneCall2, count 3
Writing MyModule_PhoneCall2, count 4

• in the other terminal run the rtiddsprototyper like this

./rtiddsprototyper -cfgFile MySubscriber.xml -luaFile MySubscriber.lua
 RTI Connext Prototyper_with_Lua-Eng_build built with NDDS version: 5.1.0 (Core: 1.7a.00, C: 1.7a.00, C++: 1.7a.00)
 Copyright 2012 Real-Time Innovations, Inc.
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Member1[2][2]= 1
  Member1[2][2]= 2
  Member1[2][2]= 3
  Member1[2][2]= 4
 Finishing Prototyper..

Please let me know if this answer your question, 

Best,
   Gianpiero Napoli

Hello Ken,

I am glad I could help. Now, for your next question: what you are doing in XML should be equivalent to what you are doing in C++. As described in the documentation here, if the add_peer() method is called before the DomainParticipant is enabled, the peer description will simply be added to the list that was populated by DDS_DiscoveryQosPolicy::initial_peers;

So what you are doing should be equivalent.

I would like to add, that even writing in C++ (or any other language) you can still use the XML file for QoS configuration! 

Let me know if you have more doubts.

Best,
 Gianpiero