query a static image camera and animate it

MJPEGViewController.m

//
//  MJPEGViewController.m
//  iMocs
//
//  Created by akh on 2018-10-29.
//  Copyright ? 2018 akh. All rights reserved.
//

#import "MJPEGViewController.h"

@interface MJPEGViewController ()
- (IBAction)reloadTouched:(id)sender;
@property (weak, nonatomic) IBOutlet UIView *connectedView;
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@property (nonatomic, strong) dispatch_source_t timerSource;
@property (nonatomic, strong) NSURLSession *session;
@property (nonatomic, strong) NSTimer *timer;
@end

@implementation MJPEGViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.
  NSURLSessionConfiguration *config = [NSURLSessionConfiguration ephemeralSessionConfiguration];
  config.timeoutIntervalForResource = 10;
  config.timeoutIntervalForRequest = 0.3;
  self.session = [NSURLSession sessionWithConfiguration:config];
}

- (void) fetchOne {
  dispatch_semaphore_t sem = dispatch_semaphore_create(0);
  NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://192.168.12.1:8080/?action=snapshot"]] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    if (error != nil) {
      NSLog(@"error dl image %@", [error localizedDescription]);
      dispatch_async(dispatch_get_main_queue(), ^{
        self.connectedView.backgroundColor = [UIColor redColor];
      });
    }
    
    UIImage *downloadedImage = [UIImage imageWithData:data];
    if (downloadedImage != nil) {
      dispatch_async(dispatch_get_main_queue(), ^{
        self.imageView.image = downloadedImage;
        self.connectedView.backgroundColor = [UIColor greenColor];
      });
    }
    dispatch_semaphore_signal(sem);
  }];
  
  [dataTask resume];
  dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
}

- (void) play {
  [self.timer invalidate];
  self.timer = [NSTimer scheduledTimerWithTimeInterval:0.125
                                                target:self
                                              selector:@selector(fetchOne)
                                              userInfo:nil
                                               repeats:YES];
}

- (void) stop {
  self.connectedView.backgroundColor = [UIColor redColor];
  [self.timer invalidate];
}

- (void) viewDidAppear:(BOOL)animated {
  [super viewDidAppear:animated];
  [self play];
}

- (void)viewDidDisappear:(BOOL)animated {
  [super viewDidDisappear:animated];
  [self stop];
}

- (IBAction)reloadTouched:(id)sender {
  [self stop];
  [self play];
}

@end