The unit described in this article show how we can start or stop a NT service by programming, or getting the location of its binary implentation.

unit SvcUtils;

// Written by Bertrand Goetzmann (http://www.object-everywhere.com)
// Keywords : Service, OpenSCManager, OpenService, CloseServiceHandle, QueryServiceConfig, StartService, QueryServiceStatus, ControlService

interface

// This function returns the entire path location of the implementation of the given name service
function GetBinaryPathName(const ServiceName: string): string;

// This function starts the service with the given service name
procedure StartService(const ServiceName: string);

// This function stops the service with the given service name
procedure StopService(const ServiceName: string);


implementation

uses SysUtils, WinSvc;

function GetBinaryPathName(const ServiceName: string): string;
var
  SvcMgr, Svc: Integer;
  QuerySvc: TQueryServiceConfig;
  BytesNeeded: Cardinal;

  Buffer: PQueryServiceConfig;
begin
  // Establish a connection to the service control manager
  SvcMgr := OpenSCManager(nil (*MachineName*), nil (*DatabaseName*), SC_MANAGER_ALL_ACCESS);
  try
    if SvcMgr = 0 then RaiseLastOSError;

    Svc := OpenService(SvcMgr, PChar(ServiceName), SERVICE_ALL_ACCESS);
    if Svc = 0 then RaiseLastOSError;
    try
      // Make a call to know the number of bytes needed
      QueryServiceConfig(Svc, @QuerySvc, 0, BytesNeeded);

      GetMem(Buffer, BytesNeeded);
      try
        if not QueryServiceConfig(Svc, Buffer, BytesNeeded, BytesNeeded) then
          RaiseLastOSError;

        Result := PQueryServiceConfig(Buffer).lpBinaryPathName;
      finally
        FreeMem(Buffer);
      end;
    finally
      CloseServiceHandle(Svc);
    end;
  finally
    CloseServiceHandle(SvcMgr);
  end;
end;

procedure StartService(const ServiceName: string);
var
  SvcMgr, Svc: Integer;
  ServiceArgVectors: PChar;
begin
  // Establish a connection to the service control manager
  SvcMgr := OpenSCManager(nil (*MachineName*), nil (*DatabaseName*), SC_MANAGER_ALL_ACCESS);
  try
    if SvcMgr = 0 then RaiseLastOSError;

    Svc := OpenService(SvcMgr, PChar(ServiceName), SERVICE_ALL_ACCESS);
    if Svc = 0 then RaiseLastOSError;
    try
      if not WinSvc.StartService(Svc, 0 (*NumServiceArgs*), ServiceArgVectors) then
        RaiseLastOSError;
    finally
      CloseServiceHandle(Svc);
    end;
  finally
    CloseServiceHandle(SvcMgr);
  end;
end;

procedure StopService(const ServiceName: string);
var
  SvcMgr, Svc: Integer;
  ServiceStatus: _SERVICE_STATUS;
begin
  // Establish a connection to the service control manager
  SvcMgr := OpenSCManager(nil (*MachineName*), nil (*DatabaseName*), SC_MANAGER_ALL_ACCESS);
  try
    if SvcMgr = 0 then RaiseLastOSError;

    Svc := OpenService(SvcMgr, PChar(ServiceName), SERVICE_ALL_ACCESS);
    if Svc = 0 then RaiseLastOSError;
    try
      // if not QueryServiceStatus(Svc, ServiceStatus) then
      //  RaiseLastOSError;
      // You can test the ServiceStatus.dwCurrentState field

      if not ControlService(Svc, SERVICE_CONTROL_STOP, ServiceStatus) then
        RaiseLastOSError;
    finally
      CloseServiceHandle(Svc);
    end;
  finally
    CloseServiceHandle(SvcMgr);
  end;
end;

end.