Go to the Windows Service series & mdash; and add COM and Windows interfaces to windows Services

Go to Windows Service series-add COM and Windows interfaces to windows Services

When running a Windows service, we usually choose to run it in Non-window or non-Console mode. In this way, it is just a background program, there is no interface for interaction.

So what should we do when we want to interact with the Windows Service in real time?

Quick Solution for adding real-time interaction to Windows Services

Windows is a process, and the program we use for interaction is another process. Real-time interaction with Windows Services is actually a problem of inter-process communication. All inter-process communication solutions are basically applicable to real-time interaction solutions, such as Socket, shared memory, pipelines, and COM.

Among these solutions, the development of COM is the fastest, because we add COM interfaces to the ATL-based Windows service.

COM Introduction

The Component Object Model (COM) is a set of binary interface standards for Microsoft software components. This makes inter-process communication and dynamic object creation across programming languages possible. COM is the basis of a number of Microsoft technologies and frameworks, including OLE, OLE Automation, ActiveX, COM +, DCOM, Windows shell, DirectX, and Windows Runtime. For details, refer to component object model.

Add COM interface to service

For details about how to create an ATL-based Windows Service, refer to "go to the Windows Service series" to create a Windows service.

Next, add a COM interface to the service.

First, add an ATL simple object to the project, as shown below:

ServiceComTest. idl

The file content is as follows:

import "oaidl.idl";import "ocidl.idl";[    object,    uuid(4DDE5CA3-F5D7-4BC3-9045-E697297C5530),    dual,    nonextensible,    pointer_default(unique)]interface IIServiceComTest : IDispatch{};[    uuid(54A347BA-7689-4578-A346-C96D924BD637),    version(1.0),]library ServiceComTestLib{    importlib("stdole2.tlb");    [        uuid(C264868C-91E7-4BFE-8DD9-32D0804E44F6)            ]    coclass IServiceComTest    {        [default] interface IIServiceComTest;    };};

This idl file is used to define the COM interface.

Next, add a new method to the interface.

In the Class View, find the generated interface IIServiceComTest:

Interface IIServiceComTest: IDispatch {[id (1), helpstring ("adding two integers")] HRESULT add ([in] LONG x, [in] LONG y, [out, retval] LONG * result );};Implement COM interface

The method we add to the COM interface is only a declaration and description. We must implement this method before other processes can communicate with this service.

You can find this method in the IServiceComTest. cpp file:

STDMETHODIMP CIServiceComTest: add (LONG x, LONG y, LONG * result) {// TODO: add the implementation code return S_ OK here ;}

This method is implemented as follows:

STDMETHODIMP CIServiceComTest::add(LONG x, LONG y, LONG* result){    *result = x + y;    return S_OK;}

In this way, a complete COM interface and its implementation are completed. Next, you need to call this interface through the test program for testing.

Call the COM interface

Create a basic console program and test the initialization test code. The Code is as follows:

#include "..\ServiceComTest\ServiceComTest_i.c"#include "..\ServiceComTest\ServiceComTest_i.h"#include <iostream>using namespace std;int _tmain(int argc, _TCHAR* argv[]){    IIServiceComTest* test;    CoInitialize(NULL);    auto hresult = CoCreateInstance(CLSID_IServiceComTest,        NULL,        CLSCTX_LOCAL_SERVER | CLSCTX_INPROC_HANDLER,        IID_IIServiceComTest,        (void**)&test);    LONG x = 1;    LONG y = 2;    LONG result = 0;    hresult = test->add(x, y, &result);    cout << "result is " << result << endl;    system("pause");}

Here, it is just a demo program that skips code error handling.

Run the program and get the correct result. result is 3. The result is as follows:

References

Step by Step COM Tutorial

COM in C ++

COM (C ++) programming tutorials

C/C ++ COM Code Example: Reading Messages Asynchronously

Series links

Go to the Windows Service series-create a Windows Service

How to register and uninstall the Debug and Release versions of the Windows Service series

Go to the Windows Service series -- Why Windows service fails to be started without the COM interface and the Solution

Go to the Windows Service series-analysis of service running and stopping Processes

Turn to the Windows Service series-Tips for Windows Services

Go to Windows Service series-command line management for Windows Services

Fun with Windows Service series-Windows Service Startup timeout

Go to the Windows Service series-use Boost. Application to quickly build Windows Services

Go to Windows Service series-add COM interfaces to Windows Services