Bitcoin curl no reply
You are trying to call the RPC interface incorrectly.  Your curl - 

$ curl --digest -u rpcusername:rpcpassword -X POST 127.0.0.1:8332/json_rpc -d "{\"jsonrpc\":\"2.0\",\"id\":\"0\",\"method\":\"getwalletinfo\"}" -H 'Content-Type:application/json'


has an incorrect path 127.0.0.1:8332/json_rpc you are posting to.  You should create your curl request with the following path - 127.0.0.1:8332/.

Working example, printing verbosely with -v

$ curl -v --digest -u rpcusername:rpcpassword -X POST 127.0.0.1:8332/ -d "{\"jsonrpc\":\"2.0\",\"id\":\"0\",\"method\":\"getwalletinfo\"}" -H 'Content-Type:application/json'