Problem with SSL GRPS on .Net Core 5.0

New To Flow
1

Hi

I am trying to connect to flow grpc.
And when I use it, I am facing such errors

Grpc.Core.RpcException: 'Status(StatusCode=“Unavailable”, Detail="Error starting gRPC call.
HttpRequestException: The SSL connection could not be established, see inner exception. IOException:
Cannot determine the frame size or a corrupted frame was received.
the urls which I used to connect to grpc https://access.mainnet.nodes.onflow.org:9000
or https://access.devnet.nodes.onflow.org:9000, both have same errors

Note: I want only read information from flow.

Could you please explain:

  1. what is correct way of connecting to flow(any WORKING examples)?
  2. do I need to sign up and recive any tokens to use flow?