Watching contract events with Infura

[dapplion]

Issue #13 shared the inability to listen to contract events through JSON-RPC calls using Infura a year ago. Does any team member have a suggestion on how to achieve so currently? Thank you so much.

[ncocchiaro]

We support websocket endpoints on mainnet, ropsten and rinkeby now that allow you to listen to events:

wss://mainnet.infura.io/ws
wss://ropsten.infura.io/ws
wss://rinkeby.infura.io/ws

The alternative would be to call eth_getLogs starting at a block that's relevant to the contract.

[StarNeit]

@ncocchiaro , would you please explain more details how to watch contract events?

[StarNeit]

I am using Infura to mint tokens, but I am not able to find a way to confirm whether transaction is succeeded or failed.

const txhash = "0x5bba2e5cbe643b9a6ccbc5664c737fb411a79e0324c53c4559f081c47e2c6f54"; web3.eth.getTransactionReceipt(txhash).then(txObj => { console.log(txObj); }).catch(err => { console.log(err); })

Error: Web3ProviderEngine does not support synchronous requests.

Please let me know how to watch events when using infura, thank you so much.

[ncocchiaro]

@StarNeit an example of how to use Pub/Sub via websockets to listen for new blocks can be found in #29 (which as it seems you've found by now) and I'm pasting it below. You should be able to adapt that for logs, following the geth pub/sub documentation at https://github.com/ethereum/go-ethereum/wiki/RPC-PUB-SUB.

#!/usr/bin/env node
const Web3 = require('web3');

const web3 = new Web3(new Web3.providers.WebsocketProvider('wss://mainnet.infura.io/ws'));

const subscription = web3.eth.subscribe('newBlockHeaders', (error, blockHeader) => {
  if (error) return console.error(error);

  console.log('Successfully subscribed!', blockHeader);
}).on('data', (blockHeader) => {
  console.log('data: ', blockHeader);
});

// unsubscribes the subscription
subscription.unsubscribe((error, success) => {
  if (error) return console.error(error);

  console.log('Successfully unsubscribed!');
});

The other issue with Web3ProviderEngine is unrelated and due to Web3 not returning promises, so you're effectively calling a method synchronously, which is disallowed.

[StarNeit]

@ncocchiaro , Thank you for your kind explanation.
But, how can I get transaction list of my own contract?
I only would like to get event of my contract. Is that possible?

[StarNeit]

@ncocchiaro , Thank you.

I solved problem by using getTransactionReceipt. 👍 👍 👍

[ncocchiaro]

Great, let us know if you have other issues.

[vijaytabhatt]

@StarNeit can you please tell me how did you solve by getTransactionReceipt?
I am writing a contract where listing to events in my contract is very important
how do we listen to our custom events using websocketprovider?

[sulliwane]

@ncocchiaro is kovan wss://kovan.infura.io/ws on the roadmap?

[ncocchiaro]

We plan on adding support for the Parity pub/sub interface (all the existing websocket endpoints are backed by Geth), at that point it's possible we'll add a Kovan endpoint. In the meantime if you require a PoA network and don't strictly require Parity my suggestion is to try Rinkeby.

[sulliwane]

Thanks for the update. One more question, it seems the websocket interface doesn't implement non pub/pub methodes (like getBlock()...) I suppose it's by design ?

[walfridosp]

I'm trying to use:

var subscription = web3.eth.subscribe('logs', {
    address: ['0x06012c8cf97bead5deae237070f9587f8e7a266d', '0x06012c8cf97bead5deae237070f9587f8e7a266e'],
    topics: null
}, function(error, result){
    if (!error)
        console.log(result);
})
.on("data", function(log){
    console.log(log);
})
.on("changed", function(log){
});

But I'm getting the following error:

Uncaught Error: Provided address ... is invalid, the capitalization checksum test failed

As per the documentation: https://web3js.readthedocs.io/en/1.0/web3-eth-subscribe.html#subscribe

address - String|Array: An address or a list of addresses to only get logs from particular account(s).

Can I pass an Array of addresses instead of a single address?

[rhlsthrm]

If you want to watch contract events, use this API: http://web3js.readthedocs.io/en/1.0/web3-eth-contract.html#contract-events

myContract.events.MyEvent({
    filter: {myIndexedParam: [20,23], myOtherIndexedParam: '0x123456789...'}, // Using an array means OR: e.g. 20 or 23
    fromBlock: 0
}, function(error, event){ console.log(event); })
.on('data', function(event){
    console.log(event); // same results as the optional callback above
})
.on('changed', function(event){
    // remove event from local database
})
.on('error', console.error);

[timxor]

Hey @ncocchiaro ! Long time no see :D Is there still no support for a truffle-kovan endpoint from infura?! Thanks man, hope you have been well~

[ncocchiaro]

Hey @tcsiwula, we have the RPC endpoint at https://kovan.infura.io/YOUR_API_KEY but not yet a websockets endpoint for Kovan.

[ramxis]

I am having the same issue, the problem is i cannot use Websockets as I am using web3 0.20.6, as when i use web3 1.0 my constant function gives me the error "UnhandledPromiseRejectionWarning: Error: Couldn't decode uint256 from ABI: 0x" when using infura. Since i was not able to resolve the issue with constant functions when using infura so i switched to web3 0.20.6 which works fine for everything except events. Both events and Constant functions works fine if i use ganache but as soon as i connect to infura every thing breaks down. Please tell me how can i watch or get events using infura and web3 v 0.20.6?

[stefek99]

Micro rant in a related issue: #13 (comment)

Now realizing I need to update my web3.js, TypeError: Web3.providers.WebsocketProvider is not a constructor.

Trying to set up super basic demo using web3.js 1.0.0 and const web3 = new Web3(new Web3.providers.WebsocketProvider('wss://ropsten.infura.io/ws'));

Sample code:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Metamask + WebSockets + web3.js 1.0.0</title>

    <!-- USING THIS VERSION: https://github.com/ethereum/web3.js/blob/1.0/dist/web3.js -->
    <script src="lib/web3-v1.0.0-beta.34.js"></script>

    <script>
    var address = "0x2328bc22d5705b2cde99e02a780e2fecdca4ad6b"; // https://ropsten.etherscan.io/address/0x2328bc22d5705b2cde99e02a780e2fecdca4ad6b
    var ABI = [{"constant":true,"inputs":[],"name":"timestampEnd","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"howManyGuaranteed","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"addr","type":"address"}],"name":"getPosition","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"bid","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":true,"inputs":[],"name":"HEAD","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"initialPrice","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"contributors","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"instructions","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"beneficiary","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"bids","outputs":[{"name":"prev","type":"uint256"},{"name":"next","type":"uint256"},{"name":"value","type":"uint256"},{"name":"contributor","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"getGuaranteedContributorsLenght","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"finalize","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"addr","type":"address"}],"name":"refundOnBehalf","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"lastBidID","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"refund","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"howMany","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"bids","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"guaranteedContributors","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"increaseTimeIfBidBeforeEnd","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"description","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"getPosition","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_description","type":"string"}],"name":"setDescription","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"price","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"_contribution","type":"uint256"},{"name":"_startSearch","type":"uint256"}],"name":"searchInsertionPoint","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"LIMIT","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"finalized","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"priceGuaranteed","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"getAccountListLenght","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"TAIL","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"increaseTimeBy","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"accountsList","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"winner","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"guaranteedContributions","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_instructions","type":"string"}],"name":"setInstructions","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"inputs":[{"name":"_price","type":"uint256"},{"name":"_description","type":"string"},{"name":"_timestampEnd","type":"uint256"},{"name":"_beneficiary","type":"address"},{"name":"_howMany","type":"uint256"},{"name":"_howManyGuaranteed","type":"uint256"},{"name":"_priceGuaranteed","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"},{"payable":true,"stateMutability":"payable","type":"fallback"},{"anonymous":false,"inputs":[{"indexed":false,"name":"addr","type":"address"},{"indexed":false,"name":"value","type":"uint256"},{"indexed":false,"name":"timestamp","type":"uint256"}],"name":"GuaranteedBid","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"name":"number","type":"uint256"}],"name":"LogNumber","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"name":"text","type":"string"}],"name":"LogText","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"name":"addr","type":"address"}],"name":"LogAddress","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"bidder","type":"address"},{"indexed":true,"name":"price","type":"uint256"},{"indexed":true,"name":"timestamp","type":"uint256"}],"name":"BidEvent","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"addr","type":"address"},{"indexed":true,"name":"value","type":"uint256"},{"indexed":true,"name":"timestamp","type":"uint256"}],"name":"Refund","type":"event"}];

    const web3 = new Web3(new Web3.providers.WebsocketProvider('wss://ropsten.infura.io/ws'));

    setTimeout(function() {
      var contract = new web3.eth.Contract(ABI, address);

      contract.methods.getAccountListLenght().call(function(err, res) {
        console.log(err, res);
      });

    }, 2000); // 2 seconds to initiatilize the thing

    </script>

  </head>
  <body>
  
  </body>
</html>

WebSocket connection to 'wss://ropsten.infura.io/ws' failed: Error during WebSocket handshake: Sent non-empty 'Sec-WebSocket-Protocol' header but no response was received
WebsocketProvider
connection not open on send()

[acidfreako]

yep i got the same error , i am asking the same question on gitter channel.

[woshidama323]

Have you fixed this problem ?

[acidfreako]

Yes I did downgrades Yk beta version 33 and solved the problem

[wodxumingxu]

i got the same error, what is Yk you refers to? @acidfreako

[JeeChoi]

the problem/fix(?) is described here: web3/web3.js#1559
like @acidfreako said, you need to downgrade web3.js beta to version 33

[acidfreako]

@wodxumingxu yes downgrading the web3 from beta 34 to 33 helped

[ghost]

@ncocchiaro Can you already tell when there will be support for websockets on Kovan?

[ncocchiaro]

Good timing! We now have a wss://kovan.infura.io/ws endpoint, and have just published new documentation on the websocket API: https://infura.io/docs/wss/introduction. Please create a new issue if you see any problems.