Invalid JSON RPC response when calling a function

Question

I've made a web3js script in a wordpress website, but when executing the following code, I get an invalid JSON RPC response.

var Web3 = require("web3");
var web3 = new Web3();
web3.setProvider(new web3.providers.HttpProvider("https://ropsten.infura.io/xxxxxxxxxxx"));
var accounts = web3.eth.accounts;
var abi=[{"constant":false,"inputs":[{"name":"document","type":"string"},{"name":"timestamp","type":"uint256"}],"name":"notarize2","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"name":"document","type":"string"}],"name":"checkDocument","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"proof","type":"bytes32"},{"name":"timestamp","type":"uint256"}],"name":"storeProof","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"name":"source","type":"string"}],"name":"stringToBytes32","outputs":[{"name":"result","type":"bytes32"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"proof","type":"bytes32"}],"name":"hasProof","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}];
web3.eth.defaultAccount="XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
var poe = web3.eth.contract(abi).at("YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY");
console.log(poe.address);
result="test";
var today = new Date();
var todayI = today.getFullYear()*10000+ (today.getMonth()+1)*100+today.getDate();
console.log(todayI);                     
poe.notarize2(result,todayI,{gas:2000000});

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The setup works perfect through testrpc (localhost) and through Remix / Metamask I could verify that the contract is correctly deployed on Ropsten and is working fine.

Any ideas? this is the first time I'm trying this.

Answer 1

Try setting the account to a string address instead. As Smarx,public node as infura don't handle private method like accounts. Also when using metamask this account set aswell as web.accounts[0]

Answer 2

I'm not sure this is your only problem, but you haven't specified an account from which to make this transaction. Infura, as a public node, can't hold anyone's private keys, so it knows of no accounts.

If you want the viewer of the page to make the transaction, you'll need to use something like MetaMask instead of directly connecting to a node.

If you want to somehow make the transaction with your own account, that would have to happen server-side, since you can't give viewers of your website access to your private key.

https://programtheblockchain.com/posts/2017/12/13/building-decentralized-apps-with-ethereum-and-javascript/ might help, particularly the "Connecting to a Node" section, which explains the role of MetaMask.