Handling Events Emitted By Smart Contract On Matic Network

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1

I am trying to listen to and handle events that are emitted by our smart contract. With our contract on Ropsten I can use Infura’s WebSocket gateway (wss://ropsten.infura.io/ws), but there is no such Infura gateway for the Matic Network.

How may I handle smart contract events emitted on the Matic sidechain?

Edit: I should note the reason we are using the Infura provider is because we need to handle the events on the server, where of course we don’t have access to MetaMask.

2

Matic also provides websocket gateway which you can use to listen to events, just switch the RPC url to https://testnet.matic.network. Alternatively you can use dagger to listen to events on both Ropsten and Matic.

3

Great, thanks for the info!

Steve

2 Likes
4

Should the WebSocket gateway be proceeded by “https”? I tried “https://testnet.matic.network” with no luck. I then tried “wss://testnet.matic.network”, but still no luck.

Steve

5

If you are using https://testnet2.matic.network, dagger endpoint for Testnet2 is wss://matic.dagger2.matic.network. You can also play with it here: https://matic.network/dagger/play

6

@steve You can use the following:

  1. For RPC connections : https://testnet2.matic.network
  2. For Websocket connections: wss://testnet2.matic.network
  3. For dagger: wss://matic.dagger2.matic.network
  4. For viewing transaction status : https://explorer.testnet2.matic.network
7

Thank you, wss://matic.dagger2.matic.network for Dagger is working great.

But I’m having trouble obtaining the logs data. When I use:

dagger.on('latest:log/' + <address />, function(result) {
    console.log(result);
});

I get an object containing various data, including the blockHash, transactionHash, blockNumber, etc. But I’m unable to obtain the logs data. However, when I check Remix I see the data is being returned. For example:

logs: [
    {
	    "from": "0xabff528a6b58fa554d46aec318f025212be89a96",
	    "topic": "0x11a679e84067f3949dee0d8352a5dd5ec9ebd4d70500c2bdd23f0d78abd3f61d",
	    "event": "SpinResult",
	    "args": {
		    "0": "224",
		    "1": "0",
		    "_number": "224",
		    "_amountWin": "0",
		    "length": 2
	    }
    }
]

Is being returned in Remix, but not from Dagger. How may I obtain this data?

8

@steve

As discussed in our TG chat, you can use the event config log/contractAddress/filter/topic0/topic1 for finer querying. You will need to add the indexed parameter to your events in the contract for this.

9

Thanks, adding the indexed parameter got it working.