The operation couldn’t be completed. (OSStatus error -9847.)

I am trying to use GraphQL Subscription on iOS simulator and I get error saying The operation couldn’t be completed. (OSStatus error -9847.)

I am using Apollo iOS 1.9.0

Is this a simulator issue? I don’t have a real device to test on

Here is my code

import Apollo
import Foundation
import ApolloWebSocket

class Network {
  static let shared = Network()

    private(set) lazy var apollo: ApolloClient = {
        let client = URLSessionClient()
        let cache = InMemoryNormalizedCache()
        let store = ApolloStore(cache: cache)
        let url = URL(string: "http://localhost:4000/graphql")!
        let transport = RequestChainNetworkTransport(interceptorProvider: DefaultInterceptorProvider(client: client, shouldInvalidateClientOnDeinit: true, store: store), endpointURL: url)

my ViewController is as follows

import UIKit
import Apollo
import MyUserAPI

class ViewController: UIViewController {
    var activeSubscription: Cancellable?

    override func viewDidLoad() {
        // Do any additional setup after loading the view.
    func startSubscription() {
           activeSubscription = Network.shared.apollo.subscribe(subscription: MyUserSubscription()) { [weak self] result in
               guard self != nil else {
               switch result {
               case .success(let graphQLResult):
                   if let user = {
                   if let errors = graphQLResult.errors {
                       debugPrint(errors[0].message ?? "Error")
               case .failure(let error):


        let webSocket = WebSocket(
            url: URL(string: "wss://localhost:4000/graphql")!,
            protocol: .graphql_ws

        let webSocketTransport = WebSocketTransport(websocket: webSocket)

        let splitTransport = SplitNetworkTransport(
            uploadingNetworkTransport: transport,
            webSocketNetworkTransport: webSocketTransport

        return ApolloClient(networkTransport: splitTransport, store: store)

Here is the complete repo

For the benefit of others, we’ve taken up debugging this in a repo issue. You can follow that for a resolution.