Implement automatic check for missing local network access

[wutschel]

I suspect that many of the users who report the App is not working, not working after update or cannot connect simply face the problem of missing local network access. Sadly, this is sometimes not easy to resolve due ani iOS internal bug. In such case users need workaround like

• remove and reinstall app
• delete the network settings and restart

To improve this situation the Remote App can implement an automatic check for local network access. If not granted, a message / popup with details on how to resolve the issue can be shown. The implementation can be taken from https://stackoverflow.com/questions/67058134/objective-c-ios-14-how-to-do-network-privacy-permission-check

// LocalNetworkPrivacy.h

@interface LocalNetworkPrivacy : NSObject

- (void)checkAccessState:(void (^)(BOOL))completion;
    
@end

// LocalNetworkPrivacy.m

#import <UIKit/UIKit.h>
//#import "LocalNetworkPrivacy.h"

@interface LocalNetworkPrivacy () <NSNetServiceDelegate>

@property (nonatomic) NSNetService *service;
@property (nonatomic) void (^completion)(BOOL);
@property (nonatomic) NSTimer *timer;
@property (nonatomic) BOOL publishing;

@end

@implementation LocalNetworkPrivacy

- (instancetype)init {
    if (self = [super init]) {
        self.service = [[NSNetService alloc] initWithDomain:@"local." type:@"_lnp._tcp." name:@"LocalNetworkPrivacy" port:1100];
    }
    return self;
}

- (void)dealloc {
    [self.service stop];
}

- (void)checkAccessState:(void (^)(BOOL))completion {
    self.completion = completion;
    
    self.timer = [NSTimer scheduledTimerWithTimeInterval:2 repeats:YES block:^(NSTimer * _Nonnull timer) {
        if (UIApplication.sharedApplication.applicationState != UIApplicationStateActive) {
            return;
        }
        
        if (self.publishing) {
            [self.timer invalidate];
            self.completion(NO);
        }
        else {
            self.publishing = YES;
            self.service.delegate = self;
            [self.service publish];
        }
    }];
}


#pragma mark - NSNetServiceDelegate

- (void)netServiceDidPublish:(NSNetService *)sender {
    [self.timer invalidate];
    self.completion(YES);
}

@end

Calling the check:

LocalNetworkPrivacy* localNetworkPrivacy = [LocalNetworkPrivacy new];
[localNetworkPrivacy checkAccessState:^(BOOL granted) {
    NSLog(@"Granted: %@", granted ? @"YES" : @"NO");
}];