NWPathMonitor error when monitoring the internet connection

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I'm working on a Swift app where I need to know when the device is connected to the internet or not and I implemented the following code to do that.

import Foundation
import Network

class NetworkMonitor: ObservableObject{
    
    static let shared = NetworkMonitor()
    private let queue = DispatchQueue.global()
    private let monitor: NWPathMonitor
    public private(set)var isConnected :Bool=false
    public private(set)var connectionType :ConnectionType = .unknown
    
    enum ConnectionType{
        case wifi
        case cellular
        case unknown

    }
    
    init(){
        monitor = NWPathMonitor()
    }
    
    public func startMonitoring(){
     
            monitor.pathUpdateHandler={[weak self] path in
                self?.isConnected=path.status == .satisfied
                self?.getConnectionType(path)
            }
        
        monitor.start(queue: queue)

    }
    
    public func stopMonitoring(){
        monitor.cancel()
    }
    public func getConnectionType(_ path: NWPath){
        if(path.usesInterfaceType(.wifi)){
            connectionType = .wifi
        }else if(path.usesInterfaceType(.cellular)){
            connectionType = .cellular
        }else{
            connectionType = .unknown
        }
    }
}

The problem arises when the function startMonitoring() is called. Everything seems to work fine but I get this error messages in the console


2022-12-01 13:04:37.327650+0100 Luuk[11692:1287784] [] nw_path_evaluator_set_queue Client error: set queue after starting
2022-12-01 13:04:37.328799+0100 Luuk[11692:1287784] [] nw_path_evaluator_set_queue Client error: set queue after starting, dumping backtrace:
        [arm64] libnetcore-2750.120.19.0.1
    0   libnetwork.dylib                    0x0000000181950d4c __nw_create_backtrace_string + 192
    1   libnetwork.dylib                    0x0000000181166f70 nw_path_evaluator_set_queue + 304
    2   libnetwork.dylib                    0x00000001811841f8 nw_path_monitor_set_queue + 96
    3   libswiftNetwork.dylib               0x00000001f0846ee4 $s7Network13NWPathMonitorC5start5queueySo012OS_dispatch_E0C_tF + 72
    4   Luuk                                0x0000000104cfa418 $s4Luuk14NetworkMonitorC15startMonitoringyyF + 216
    5   Luuk                                0x0000000104c7d010 $s4Luuk11SummaryViewV4bodyQrvgyycfU1_yyScMYccfU_ + 56
    6   Luuk                                0x0000000104c137e0 $sIeg_IeyB_TR + 48
    7   libdispatch.dylib                   0x0000000105640c70 _dispatch_call_block_and_release + 32
    8   libdispatch.dylib                   0x00000001056427c0 _dispatch_client_callout + 20
    9   libdispatch.dylib                   0x0000000105652c68 _dispatch_main_queue_drain + 1204
    10  libdispatch.dylib                   0x00000001056527a4 _dispatch_main_queue_callback_4CF + 44
    11  CoreFoundation                      0x00000001803fe800 5198FB57-5645-3B34-A49F-F32B52256CF3 + 333824
    12  CoreFoundation                      0x00000001803b8704 5198FB57-5645-3B34-A49F-F32B52256CF3 + 46852
    13  CoreFoundation                      0x00000001803cbbc8 CFRunLoopRunSpecific + 600
    14  GraphicsServices                    0x000000019c4ff374 GSEventRunModal + 164
    15  UIKitCore                           0x0000000182d3b648 3ED35565-456D-33CB-B554-6C567FA81585 + 5326408
    16  UIKitCore                           0x0000000182abcd90 UIApplicationMain + 364
    17  SwiftUI                             0x000000018821df24 5B6954AE-CE76-34AC-90F9-F7A8DEE0910F + 2359076
    18  SwiftUI                             0x000000018814be08 5B6954AE-CE76-34AC-90F9-F7A8DEE0910F + 1498632
    19  SwiftUI                             0x000000018812d0f4 $s7SwiftUI3AppPAAE4mainyyFZ + 128
    20  Luuk                                0x0000000104ce5318 $s4Luuk0A3AppV5$mainyyFZ + 40
    21  Luuk                                0x0000000104ce53c0 main + 12
    22  dyld                                0x000000010540dce4 start + 520

I searched online but there's not a lot of information about this kind of error. Any help would be much appreciated.

When I comment out the line

        monitor.start(queue: queue)

the error goes away

1

There are 1 answers

2
Jorge Poveda On BEST ANSWER

That error could be provoked by the repeated use of the same instance of NWPathMonitor after it is cancelled -as described here-.

When an instance of NWPathMonitor is cancelled, you can't use start() again. The only way would be to create a new instance.

Can you check in your code if you are trying to cancel->start with the same instance?


Also, I'd say you should maybe change the queue in which you are setting the start(), instead of global, you could set up one specific for this purpose

DispatchQueue(label: "NetworkMonitor")

or even use the main thread.