WebSocket connection failed

I am trying to implement a libp2p chat application. While creating a node , I got the below WebSocket connection errors:

WebSocket connection to ‘wss://ams-1.bootstrap.libp2p.io/ipfs/QmSoLer265NRgSp2LA3dPaeykiS1J6DifTC88f5uVQKNAd’ failed: Error during WebSocket handshake: Unexpected response code: 404

WebSocket connection to ‘wss://lon-1.bootstrap.libp2p.io/ipfs/QmSoLMeWqB7YGVLJN3pNLQpmmEk35v6wYtsMGLzSr5QBU3’ failed: Error in connection establishment: net::ERR_NAME_NOT_RESOLVED

Here is my code:

const SIGNAL_SERVER = ‘/dns4/ws-star.discovery.libp2p.io/tcp/443/wss/p2p-websocket-star/ipfs/:peer-id’


Npm version: 6.13.4
Node version: 10.18.1
Os:Ubuntu 18.04
webpack :3.11.0
libp2p-webrtc-star: 0.13.2
libp2p-websockets: 0.12.2

Please help me to resolve this issue.