OmniObjects

OmniObjects is a lightweight replacement for DCOM, suitable for many uses. It's still a alpha project, but it's being actively developed. 

You can download the lastest version here. Don't forget to check out the instructions, the release notes and the OmniObjects SourceForge project page.

Why replacing DCOM

• DCOM has complicated permission configurations;
• DCOM depends on RPC. RPC has some ports limits and it's also hard to configure;
• It's hard (some would say impossible) to configure DCOM to pass through firewalls. 
• There's no good implementation outside Microsoft Windows.
• It's closed source, you can't debug DCOM infrastructure if you find some cumbersome problem.

• OmniObjects is Internet ready. With extensible communication architecture, you can configure the ports, use TCP, UDP or HTTP and change whatever you want about communication. You can even make a new connector and send your method calls via e-mail. You don't need to find alternatives to COM just because DCOM is hated by every firewall in the whole Earth. Forget porting you code to SOAP, WCF, [insert another new buzzword here], with OmniObjects you can keep your COM objects working.
• If your program needs to make some kind of TCP/IP communication, you can host the OmniObjects within your application and make the network communication as simple as a function call, and in a object oriented way. You can make an Instant Messenger using COM, and the message send code will be as simple as pImServer->SendMessage("user123", "hi!"). Host your objects using OmniObjects and you will never need to deal with raw sockets by yourself again. Sounds wonderful, doesn't it? :-)

OmniObjects Overview

client → proxy → serialization lib → channel → serialization lib → stub → object

How to make your COM object compatible with OmniObjects

Project Status

• This über ugly web page.
• The OmniIdl is generating the proxy/stub for all oleautomation types we need.
• The refcount and QueryInterface for remote objects is working great.
• The OmniObjects DLL has a kernel, a proxy manager, a stub manager and a TCP connector.
• We have a test component and a test program. If you want to see some action, step into OmniSimpleHost.exe (the program that wait for remote clients) and into the OmniTestClient (the program that instantiate a remote object and call some methods). It's a simple and very effective way to understand how things works.
• A good COM smart pointer, omni_ptr. Since it doesn't overload the & operator, it can be put into STL containers. It has some safer methods CComPtr and _com_ptr_t lacks.

• You need Visual C++ 8 with ATL 8 to build the proxy/stub. The ATL dependency will be removed soon, but it's still there.
• We support the basic C++ types (char, short, int, etc) and the main automation types (BSTR and VARIANT, no SAFEARRAY yet). I think it's enough for most projects, but we plan to add support for this more date types later.
• OmniIdl doesn't support structs. But you can use an object instead
• We don't have preprocessor support for OmniIdl. The OmniIdl is adding common #defines to the know types list (LPCSTR, ULONG, UCHAR, etc).
• We don't support custom marshaling.
• We need a descent host, OmniSimpleHost host is "test purposes only".

• Make the ATL dependency optional, so we can port OmniObjects to other platforms and to Visual C++ Express + Microsoft Platform SDK. Porting OmniObjects to Linux is a priority.
• Support hosting components we don't have the source. All we need to do is to generate proxy/stub from a type library instead of an IDL file. We need to support custom marshaling as well.
• Host objects within Microsoft Internet Information Server (IIS) and Apache. It will make much easier to make components Internet ready, in a transparent fashion.
• Support non-COM objects from another languages, like Python and C#. We just need a translation layer for data types and a communication between the language/framework and the OmniObjects module.
• Make the code compatible with non Microsoft C++ compilers.

Things you must know before use the code

• I would like to make this code multi platform, but it isn't. You need Windows and Visual Studio 2005 to build it.
• You can't use the Express version because OmniObjects depends on ATL 8. It's easy to back port it to Visual Studio 2003, but you will not get it to work with ATL 3 (Visual C++ 6 and Visual C++ Express 2005 with Platform SDK).
• You need Boost to build OmniObjects.

Hacking and understanding

OmniIdl.exe: it's the idl compiler and proxy/stub generator. Run it against an IDL file and it will generate the proxy/stub source code and a Visual C++ 8 (Visual Studio 2005) project. There is an OmniTestComLibrary project in OmniObjects source root, you can use it to test how OmniIdl works. Running '..\..\bin\OmniIdl.exe OmniTestComLibrary.idl', will yield the following files:

• OmniTestComLibrary_OmniPS.cpp: COM DLL implementation (DllGetClassObject, etc).
• OmniTestComLibrary_OmniPS.def : functions to be exported.
• OmniTestComLibrary_OmniPS.h: Proxy/stub implementation. You can insert it into your VC7+ project if you want to compile the proxy/stub within your COM DLL.
• OmniTestComLibrary_OmniPS.vcproj: Visual C++ 8 project. Build and register and you're ready to go.

OmniObjects.dll: it's the OmniObjects runtime. The marshaller and the TCP/IP channel at implemented in this DLL. A proxy/stub DLL generated by OmniIdl.exe depends on this DLL. It has some proxy/stub declared for the internal types, but they are compiled together (the OmniObjectsInternalObject_OmniPS.h is included in this project).

OmniSimpleHost.exe: it's just an example about using the OmniObjects hosting API. 

OmniTestComLibrary.dll: it's a simple COM library used to show how to add OmniObjects support to an existent COM Project and how to generate the proxy/stub. Check for the projects build steps to see how we generated the proxy/stub code.

OmniTestClient.exe: it's a simple OmniObjects client, it calls methods provided by OmniTestComLibrary. Debug it to see how the whole magic works.

Release Notes

Version 0.4 release notes

• OmniIdl now supports the [size_is] attribute.
• The communication protocol was changed so arrays using [size_is] can be transmitted.
• The [string] attribute is now supported.
• OmniIdl now log the filename and line number when some error occurs during the code generations phase.

Version 0.3 release notes

Now you can pass objects (interface pointers) as parameters, and all the proxy/stub stuff will be done automagically. Also, several improvements was made in the code, mainly error handling and TCP connection management.

Version 0.2 release notes

First time you open the OmniObjects.sln, Visual Studio will complain that the OmniObjectsTestComLibrary_OmniPS project doesn't exists. Build the solution, right click over this project and choose to reload it. This is a proxy/stub project, and it will be generated during the OmniObjectsTestComLibrary build. After this, build it. You can remove this warning building the solution using the "vcbuild.exe" before opening it with the VS IDE.

Version 0.1 release notes

First time you open the OmniObjects.sln, Visual Studio will complain that the OmniObjectsTestComLibrary_OmniPS project doesn't exists. Build the solution, right click over this project and choose to reload it. This is a proxy/stub project, and it will be generated during the OmniObjectsTestComLibrary build. After this, build it.

There's a known memory leak in the marshaller.

The OmniObjects "Team"

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