I am running the bitcoin daemon with the following config in VirtualBox:

testnet=1
daemon=1
server=1
txindex=1
mintxfee=0.001
txconfirmtarget=1
rpcuser=lubo
rpcpassword=vranka
rpcport=18332
rpcallowip=127.0.0.1

[test]

rpcport=18332

And when I try to connect to it using the python-bitcoinrpc library:

from bitcoinrpc.authproxy import AuthServiceProxy, JSONRPCException

rpc_connection = AuthServiceProxy("http://%s:%s@127.0.0.1:18332"%("lubo", "vranka"))
best_block_hash = rpc_connection.getbestblockhash()

I get slapped with:

ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host

This is where I am stuck for several hours and I don't have the slightest clue as to what may be wrong.

This is the port configuration of my VirtualBox. I am running Windows 10 as host and Ubuntu 18.04 server as guest.

Any help or guidance is warmly welcomed.