React-Native and AutobahnJS

I am trying to set up a connection with a WebSocket server in a React-Native application using the npm package react-native-autobahnjs.

Here is my code :

import autobahn from 'react-native-autobahnjs';

class websocket extends Component {

  componentWillMount () {
    console.warn("MOUNTING MAIN COMPONENT");

    const connection = new autobahn.Connection({
        url: 'wss://myserver/ws',
        realm: 'realm1'
    });

    connection.onopen = () => {
      console.warn("onopen");
    };

    connection.onclose = (reason, details) => {
      console.warn("onclose : reason = " + reason + ", details = " + details);
    };

    console.warn("connection.open()");
    connection.open();
  }

  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          autobahn.js test page
        </Text>
      </View>
    );
  }
}

I get the following warning : onclose : reason = unsupported, details = [object Object]

What is going wrong? Thank you.