相信大家对Windows的服务并不陌生,但Windows的服务是怎么运作和创建的,我来讲讲我自己对Windows服务程序的理解。
首先来了解一下Windows的SC命令,这个命令是用来创建,修改和删除Windows服务,调用不同的参数来控制Windows服务,更详细的信息可以通过搜索引擎查询,也可以查阅相关书籍。
为了让自己对如何生成Windows服务程序的逻辑更加清晰,画出了简单的逻辑图,如下图所示
源码在文章最底部,SC创建服务需要绑定运行程序所在的文件目录,否则服务不知道去哪里找要运行的程序,运行程序要做的事情有两件,一是开启线程来监听服务控制器里对应的服务,二是运行真正要做事的代码。
调用StartServiceCtrlDispatcher函数来创建监听的线程ServiceMain,在ServiceMain函数里调用RegisterServiceCtrlHandler来创建监听器即ControlHandler来监听服务控制器里对应的服务,如果用户将服务开启,ControlHandler函数就会接受到该动作对应的参数,执行对应的操作即停止运行程序,即图中“真正要用到的代码”。
SetServiceStatus函数是用来更新服务控制管理器调用服务的状态信息,当用户开启服务时,会开始运行图中的流程,并调用SetServiceStatus来改变服务的状态,即状态列显示“已启动”。
最后在ServiceMain里运行真正要用的代码,这样就开始服务的人生了。
其实我一开始的本意不是这样的,我一开始是打算弄一个程序出来,运行该程序就自动创建服务并开启,这样就不用SC命令,更加独立化。
我正在研究这个,如果做出来了继续发布文章分享给大家,如果大家有什么意见或者建议,欢迎留言,如果你也对Windows的服务感兴趣,欢迎来写文章分享,共同进步。
#include <windows.h>
#include <stdio.h>
#define SLEEP_TIME 5000
#define LOGFILE "C:/MyServices/memstatus.txt"
SERVICE_STATUS ServiceStatus;
SERVICE_STATUS_HANDLE hStatus;
void ServiceMain(int argc, char** argv);
void ControlHandler(DWORD request);
int InitService();
int WriteToLog(char* str);
int main(int argc, char* argv[])
{
SERVICE_TABLE_ENTRY ServiceTable[2];
ServiceTable[0].lpServiceName = "MemoryStatus";
ServiceTable[0].lpServiceProc = (LPSERVICE_MAIN_FUNCTION)ServiceMain;
ServiceTable[1].lpServiceName = NULL;
ServiceTable[1].lpServiceProc = NULL;
// 启动服务的控制分派机线程
StartServiceCtrlDispatcher(ServiceTable);
}
void ServiceMain(int argc, char** argv)
{
int error;
ServiceStatus.dwServiceType =
SERVICE_WIN32;
ServiceStatus.dwCurrentState =
SERVICE_START_PENDING;
ServiceStatus.dwControlsAccepted =
SERVICE_ACCEPT_STOP |
SERVICE_ACCEPT_SHUTDOWN;
ServiceStatus.dwWin32ExitCode = 0;
ServiceStatus.dwServiceSpecificExitCode = 0;
ServiceStatus.dwCheckPoint = 0;
ServiceStatus.dwWaitHint = 0;
hStatus = RegisterServiceCtrlHandler(
"MemoryStatus",
(LPHANDLER_FUNCTION)ControlHandler);
if (hStatus == (SERVICE_STATUS_HANDLE)0)
{
// Registering Control Handler failed
return;
}
// Initialize Service
error = InitService();
if (!error)
{
// Initialization failed
ServiceStatus.dwCurrentState =
SERVICE_STOPPED;
ServiceStatus.dwWin32ExitCode = -1;
SetServiceStatus(hStatus, &ServiceStatus);
return;
}
// We report the running status to SCM.
ServiceStatus.dwCurrentState =
SERVICE_RUNNING;
SetServiceStatus (hStatus, &ServiceStatus);
MEMORYSTATUS memory;
// The worker loop of a service
while (ServiceStatus.dwCurrentState ==
SERVICE_RUNNING)
{
char buffer[16];
GlobalMemoryStatus(&memory);
sprintf(buffer, "%d", memory.dwAvailPhys);
int result = WriteToLog(buffer);
if (result)
{
ServiceStatus.dwCurrentState =
SERVICE_STOPPED;
ServiceStatus.dwWin32ExitCode = -1;
SetServiceStatus(hStatus,
&ServiceStatus);
return;
}
Sleep(SLEEP_TIME);
}
return;
}
void ControlHandler(DWORD request)
{
switch(request)
{
case SERVICE_CONTROL_STOP:
WriteToLog("Monitoring stopped.");
ServiceStatus.dwWin32ExitCode = 0;
ServiceStatus.dwCurrentState = SERVICE_STOPPED;
SetServiceStatus (hStatus, &ServiceStatus);
return;
case SERVICE_CONTROL_SHUTDOWN:
WriteToLog("Monitoring stopped.");
ServiceStatus.dwWin32ExitCode = 0;
ServiceStatus.dwCurrentState = SERVICE_STOPPED;
SetServiceStatus (hStatus, &ServiceStatus);
return;
default:
break;
}
// Report current status
SetServiceStatus (hStatus, &ServiceStatus);
return;
}
int WriteToLog(char* str)
{
FILE* log;
log = fopen(LOGFILE, "a+");
if (log == NULL)
return -1;
fprintf(log, "%s ", str);
fclose(log);
return 0;
}
int InitService(){
WriteToLog("Monitoring started.");
return true;
}