Using subscriptions from nodejs throws `"errorMessage": "AMQJS0007E Socket error:undefined.",`

I am trying to test my subscriptions in nodejs,

I am logging in first,

let cognitoId = null;
let client: any = null;

beforeAll(() => {
  global.fetch = fetch;
  Amplify.configure(AmplifyConfig);

  client = new AWSAppSyncClient({
    disableOffline: true,
    url: AmplifyConfig.aws_appsync_graphqlEndpoint,
    region: AmplifyConfig.aws_appsync_region,
    auth: {
      type: AmplifyConfig.aws_appsync_authenticationType,
      credentials: () => Amplify.Auth.currentCredentials(),
    },
  });

  return Promise.resolve()
    .then(() => Auth.signIn(USER.username, USER.password))
    .then(result => {
      expect(result.username).not.toBeNull();
      cognitoId = result.username;
    });
});

I then do a couple of mutations and queries which are all working fine, but when I try to test the subscription

let hydratedClient: any = null;
return Promise.resolve()
  .then(() => client.hydrated())
  .then(client => (hydratedClient = client))
  .then(() => {
    hydratedClient.query;

    hydratedClient
      .subscribe({
        query: NewMessageSubscription,
      })
      .subscribe({
        next: data => {
          console.log('Data', data);
        },
        onError: data => {
          console.log('Error', data);
        },
      });

    return hydratedClient
      .mutate({
        mutation: InsertMessage,
        variables: { message },
      })
      .then(result => {
        expect(result.data.insertMessage).toEqual(
          expect.objectContaining(message),
        );

        // Give it time to break
        setTimeout(done, 2000);
      });
  });

This throws an error though

    thrown: Object {
      "errorCode": 7,
      "errorMessage": "AMQJS0007E Socket error:undefined.",
      "invocationContext": undefined,
    }

[nicklaros]

confirmed using ws lib version ^4.0.0 and it works fine. but not with ^5.0.0, I guess it is related with some major version breaking changes

[undefobj]

This could be the version of the websocket lib you have installed in node as a specific polyfill is needed. If you look here: https://docs.aws.amazon.com/appsync/latest/devguide/building-a-client-app-node.html

You will see "ws": "^3.3.1".

Could you try the instructions listed on that page?