Smart Contract Event problem RPCError: got code -32601

[liuyuejiang]

When deploying the smart contract to Ropsten network, I tried to listen to the events from the contract, however, I got an error.
There's no error when deploying the same smart contract to Ganache.

E/flutter (27128): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: RPCError: got code -32601 with msg "The method eth_newFilter does not exist/is not available".
E/flutter (27128): #0      JsonRPC.call
package:web3dart/json_rpc.dart:49
E/flutter (27128): <asynchronous suspension>
E/flutter (27128): #1      _FilterEngine._registerToAPI
package:web3dart/…/core/filters.dart:232
E/flutter (27128): <asynchronous suspension>
E/flutter (27128): #2      _FilterEngine.addFilter
package:web3dart/…/core/filters.dart:222
E/flutter (27128): #3      Web3Client.events
package:web3dart/…/core/client.dart:328
E/flutter (27128): #4      _DeviceDetailPageState._listenevent
package:iotdevices/pages/detail.dart:62
E/flutter (27128): <asynchronous suspension>
E/flutter (27128): #5      _DeviceDetailPageState.initState
package:iotdevices/pages/detail.dart:125

My listening event dart code is as below:

var privatekey =
    "XXXXX";//Ropsten
final EthereumAddress contractAddr =
    EthereumAddress.fromHex('XXXX);//Ropsten

var apiUrl =
    "https://ropsten.infura.io/v3/XXX"; //Ropsten

var credentials = EthPrivateKey.fromHex(privatekey);

  _listenevent() async {
    String serveraddress = await SharedData.getServerAddress();
    if (serveraddress.length > 5) {
      apiUrl = serveraddress;
    }
    setState(() {
      client = Web3Client(apiUrl, Client());
    });
    
    var contract = await Web3.deployedcontract();
    final colorChangeEvent = contract.event('ColorChange');
    subscription = client
        .events(
            FilterOptions.events(contract: contract, event: colorChangeEvent))
        .take(4)
        .listen((event) {
      final decoded = colorChangeEvent.decodeResults(event.topics, event.data);

      final deviceid = decoded[0] as String;
      final red = decoded[1] as BigInt;
      final green = decoded[2] as BigInt;
      final blue = decoded[3] as BigInt;
      print("event:ID:$deviceid");
      print("event:red:${red.toInt()}");
      print("event:green:${green.toInt()}");
      print("event:blue:${blue.toInt()}");
      var curid = widget.curdevice.bid.toInt().toString();
      if (deviceid.contains(curid)) {
        print("this device changed!");
        var devcolor =
            TransColor.trancolor(red.toInt(), green.toInt(), blue.toInt());
        // print(widget.curdevice.green);
        if (mounted) {
          setState(() {
            currentColor = Color(devcolor);
          });
        }
        Event.eventBus.fire(new DeviceAdd(curdevices.name));
      }
    });
    await subscription.asFuture();
  }

How can I do with that error, is that the problem with https request? Thank you.

[simolus3]

Looking at the infura documentation, it seems like they only support event filters over websockets. This library doesn't support the rpc api over websockets (yet), so events sadly can't be used with infura at the time being. That's a bit unfortunate that they don't adhere to the official rpc api :/
I've created the referencing issue to implement websocket support, which I'll hopefully get done this weekend.

[liuyuejiang]

Looking at the infura documentation, it seems like they only support event filters over websockets. This library doesn't support the rpc api over websockets (yet), so events sadly can't be used with infura at the time being. That's a bit unfortunate that they don't adhere to the official rpc api :/
I've created the referencing issue to implement websocket support, which I'll hopefully get done this weekend.

Thank you very much, wish you can finish this weekend.