Get Window Number from Keyboard Event Using addGlobalMonitorForEventsMatchingMask and addLocalMonitorForEventsMatchingMask (Objective-C)

I am using addGlobalMonitorForEventsMatchingMask and addLocalMonitorForEventsMatchingMask to monitor the global as well as local keyboard events by providing a mask as NSEventMaskKeyDown. As global event monitoring requires accessibility permission, I am providing that as well, but the window number I am getting from the NSEvent* passed to the monitor as an argument as 0 always. Also, the window object in the event object is null (0x0). I also tried to get the window number from the CGEvent object in the NSEvent object, and the window number is still 0. Please help me with where I am wrong.

This is my main file for a headless application: main.m

#import <Foundation/Foundation.h>
#include "keylogger.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    AppDelegate *delegate = [[AppDelegate alloc] init];

    NSApplication * application = [NSApplication sharedApplication];
    [application setDelegate:delegate];
    [NSApp run];
  }
}

Header file: keylogger.h

#import <AppKit/AppKit.h>
#import <Foundation/Foundation.h>

@interface AppDelegate : NSObject <NSApplicationDelegate>

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification;

@end

File in which I am adding the monitors: keylogger.m

#import "keylogger.h"

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
  [NSEvent addGlobalMonitorForEventsMatchingMask:NSKeyDownMask
                     handler:^(NSEvent *event) {
    NSLog(@"%lld", (long long)event.windowNumber);
  }];
  [NSEvent addLocalMonitorForEventsMatchingMask:NSKeyDownMask handler:^NSEvent * _Nullable(NSEvent *event) {
    NSLog(@"%lld", (long long)event.windowNumber);
    return event;
  }];
}

@end

Note: In order to run it, please create a command line tool application in Xcode.