1- You have a good C programming background.
2- You are planning to write your own windows service. I guess it is good to start
from here.
1) Service Main: commonly called “ServiceMain” and the standard prototype for it is
It sends information to Service Control Manager (SCM) - which will take care of the status of the service - and it will register the service in the SCM.In the end of this function we will have a loop which will have our service.
2) Service CTRL Handler: this function will handle the standard requests from SCM and will response for its requests. The prototype of this function is:
3) Service Initialization function: this function will initialize the Service topically global variables, cleaning up stuff if needed, and preparation for the service. Note that this function should return a value to tell the SCM that Service successfully initialized.The prototype is:
Notes
Before showing an example I would like you to consider the following notes:
1- Service name should not contain spaces and it should not be long. In the given example below it was named “MyService”.
2- WINAPI is same as __stdcall and it is not really needed on some compiler. Also DWORD is equivalent for unsigned long.
3- The outputs of the service on x64 systems will be under “c:\Windows\SysWOW64”, and on x32 systems under “C:\Windows\System32”.
4- If the service requires an interactive process (like sending messages or loading forms) then go and read more about this in the references below. On some versions of windows in control panel --> system and security --> administrative tools --> services, then right click on the service and click on properties, then in the “Log On” tap check “Allow this service to interact with desktop” this may solve the problem.
5- Sometime service seems to be running nicely but it is not behaving as it should, well in this case we should consider the permissions give to this service, specially if we are reading/writing, a great tool called “Procmon” available on Microsoft website allow us to monitor the process so we can debug it, after installing run it and select PID filter to display your service behaviors only.
6- Each service executes in the security context of a user account, and it can be “LocalService”, “NetworkService”, or LocalSystem, every account has different privileges. These accounts do not have passwords.
7- A command-line utility, sc.exe also can be used to control services. Its commands correspond to the functions provided by the SCM. It Service (like example below) does not have “ServiceInstall” function then we would use this tool to install it.
8- Windows Vista/7 has a security feature called “Session 0 Isolation” which means service runs on Session 0 and regular user runs on session 1, and they can’t send each other messages, so it could be a problem for some services, as solution CreateProcessAsUser function may does the job.
9- The example compiled and tested under windows 7 ultimate x64 with minGW- GCC version 4.6.1.
10- If compiler did not detect the ” _WIN32_WINNT” declaration automatically then for windows 7 it is (0x0601), Vista (0x0600), and XP (0x0501).
11- Text editors can read and write files using at least the different ASCII CR/LF conventions. The text editor
Notepad is not one of them so it would be better to use Wordpad if “myRamInfo.txt” does not seem to have proper format.
Example
/**************************************************************
In
this example, the function WriteMemInfo() will write information
about available physical memory(RAM) on the system. The file
myRamInfo.txt will be updated every 5 seconds.
**************************************************************/
//#define
_WIN32_WINNT 0x0501 // for XP
//#define
_WIN32_WINNT 0x0601 // for 7
//#define
_WIN32_WINNT 0x0600 // for Vista
#include
<windows.h>
#include
<stdio.h>
SERVICE_STATUS
ServiceStatus;
SERVICE_STATUS_HANDLE
ServiceStatusHandle;
DWORD
ServiceInitialization(DWORD argc, LPTSTR *argv, DWORD
*specificError);
void
WINAPI ServiceMain(DWORD argc, LPTSTR *argv);
void
WINAPI ServiceCtrlHandler(DWORD opcode);
void
WriteMemInfo(void);
int
main(){
SERVICE_TABLE_ENTRY
DispatchTable[] = {{"MyService",
ServiceMain}, {NULL, NULL}};
if
(!StartServiceCtrlDispatcher(DispatchTable))
//WriteMemInfo("StartServiceCtrlDispatcher()
failed, error: %d.\n", GetLastError());
printf("StartServiceCtrlDispatcher()
failed, error: %ld.\n",
GetLastError());
else
printf("StartServiceCtrlDispatcher()
looks OK.\n");
return
0;
}
//
Stub initialization function...
DWORD
ServiceInitialization(DWORD argc, LPTSTR *argv, DWORD
*specificError){
//
These statments have no effect!
*argv;
argc;
specificError;
return
0;
}
void
WINAPI ServiceMain(DWORD argc, LPTSTR *argv){
DWORD
status;
DWORD
specificError;
//
Type of service, application or driver...
ServiceStatus.dwServiceType
= SERVICE_WIN32;
//
The service is starting...
ServiceStatus.dwCurrentState
= SERVICE_START_PENDING;
//
The service can be stopped & can be paused and continued.
ServiceStatus.dwControlsAccepted
= SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_PAUSE_CONTINUE;
ServiceStatus.dwWin32ExitCode
= 0;
ServiceStatus.dwServiceSpecificExitCode
= 0;
ServiceStatus.dwCheckPoint
= 0;
ServiceStatus.dwWaitHint
= 0;
ServiceStatusHandle =
RegisterServiceCtrlHandler("MyService",
ServiceCtrlHandler);
if
(ServiceStatusHandle == (SERVICE_STATUS_HANDLE)0){
printf("RegisterServiceCtrlHandler()
failed, error: %ld.\n",
GetLastError());
return;
}else
printf("RegisterServiceCtrlHandler()
looks OK.\n");
//
Initialization code goes here...return the status...
status
= ServiceInitialization(argc, argv, &specificError);
//
Handle error condition
if
(status != NO_ERROR){
//
The service is not running...
ServiceStatus.dwCurrentState
= SERVICE_STOPPED;
ServiceStatus.dwCheckPoint
= 0;
ServiceStatus.dwWaitHint
= 0;
ServiceStatus.dwWin32ExitCode
= status;
ServiceStatus.dwServiceSpecificExitCode
= specificError;
SetServiceStatus(ServiceStatusHandle,
&ServiceStatus);
return;
}
//
Initialization complete - report running status.
ServiceStatus.dwCurrentState
= SERVICE_RUNNING;
ServiceStatus.dwCheckPoint
= 0;
ServiceStatus.dwWaitHint
= 0;
if
(!SetServiceStatus(ServiceStatusHandle, &ServiceStatus)){
status
= GetLastError();
printf("SetServiceStatus()
error: %ld\n",
status);
}
else
printf("SetServiceStatus()
looks OK.\n");
//
This is where the service does its work...
while(ServiceStatus.dwCurrentState
== SERVICE_RUNNING){
WriteMemInfo();
Sleep(5000);
}
return;
}
//
Handler function - receives Opcode, calls SetServiceStatus()
void
WINAPI ServiceCtrlHandler(DWORD Opcode){
DWORD
status;
switch(Opcode){
case
SERVICE_CONTROL_PAUSE:
//
Do whatever it takes to pause here...
ServiceStatus.dwCurrentState
= SERVICE_PAUSED;
break;
case
SERVICE_CONTROL_CONTINUE:
//
Do whatever it takes to continue here...
ServiceStatus.dwCurrentState
= SERVICE_RUNNING;
break;
case
SERVICE_CONTROL_STOP:
//
Do whatever it takes to stop here...
ServiceStatus.dwWin32ExitCode
= 0;
ServiceStatus.dwCurrentState
= SERVICE_STOPPED;
ServiceStatus.dwCheckPoint
= 0;
ServiceStatus.dwWaitHint
= 0;
if
(!SetServiceStatus(ServiceStatusHandle, &ServiceStatus)){
status = GetLastError();
printf("[MY_SERVICE]
SetServiceStatus() error: %ld\n",
status);
}
printf("Leaving
MyService.\n");
return;
case
SERVICE_CONTROL_INTERROGATE:
//
Fall through to send current status.
break;
default:
//
else
printf("Unrecognized
opcode %ld.\n",
Opcode);
}
//
Send current status.
if
(!SetServiceStatus(ServiceStatusHandle, &ServiceStatus)){
status
= GetLastError();
printf("SetServiceStatus
error %ld.\n",
status);
return;
}
else
printf("SetServiceStatus()
is OK.\n");
return;
}
//
Some RAM info ...
void
WriteMemInfo(void){
MEMORYSTATUS
MemState;
MemState.dwLength = sizeof
(MemState);
//
Get Memory info
GlobalMemoryStatus(&MemState);
//
Get Time info
SYSTEMTIME
timeInfo;
GetLocalTime(&timeInfo);
FILE
*fp;
char
Wbuffer[32]="
Free RAM is: ";
sprintf(Wbuffer+strlen(Wbuffer),"%ld
MB - ",(MemState.dwAvailPhys)/(1024*1024));
sprintf(Wbuffer+strlen(Wbuffer),"%d:%d:%d
\r\n",timeInfo.wHour,timeInfo.wMinute,timeInfo.wSecond);
fp=fopen("myRamInfo.txt",
"ab");
fwrite(Wbuffer,
sizeof(Wbuffer[0]),
sizeof(Wbuffer)/sizeof(Wbuffer[0]),
fp);
fclose(fp);
return;
}
