do I need to use ws provider in order to watch events?

Question

I am using web3 version 1.0 version 26, however I can't receive any events from ganache-cli and testrpc.

  this.Contract.events.Created({},{ fromBlock: 0, toBlock: 'latest' }, function(error, event){ console.log(event); })
                        .on('data', function(event){
                              console.log(event);
                        })

this is my provider connection

this.web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'));

is httpprovider not working for the watch events? do I have to use ws provider?

Answer 1

You're correct that the HttpProvider doesn't support subscribing to events in web3.js 1.0.0. From https://web3js.readthedocs.io/en/1.0/web3.html#value:

Object - HttpProvider: The HTTP provider is deprecated, as it won’t work for subscriptions.

You will indeed need to use the WebsocketProvider (or IpcProvider for local nodes).

Answer 2

I can confirm websocket connections are supported by Ganache. I used

  web3 = new Web3()
  const eventProvider = new Web3.providers.WebsocketProvider('ws://localhost:7545')
  web3.setProvider(eventProvider)

Answer 3

Subscriptions are currently also supported through the websocket API of Infura:

const RINKEBY_WSS = "wss://rinkeby.infura.io/ws";
var provider = new Web3.providers.WebsocketProvider(RINKEBY_WSS);
var web3 = new Web3(provider);
var name = 'newBlockHeaders'; // e.g.

web3.eth.subscribe(name, (error, result) => {
        if(!error) {
            console.log(result);
        } else {
            console.log('Error:', error);          
        }
    }).on("data", function (transaction) {
        console.log(transaction);
});

See here for the documentation.