Error occured while trying to proxy Angular2 CLI, Node.js, Socket.io

I am getting error after I stop my application. How can I fix this issue? For production I am using port 3000 and for development 4200.

[HPM] Error occurred while trying to proxy request /socket.io/?EIO=3&transport=polling&t=LhNBrs9&sid=CUdJnCGXlmH0WGSyAAAA from localhost:4200 to http://localhost:3000 (ECONNRESET) (https://nodejs.org/api/errors.html#errors_common_system_errors)

My procy.conf looks like this:

proxy.conf.json

{
  "/": {
    "target": "http://localhost:3000",
    "secure": false
  }

}

via Tony