Fehler: Ungültige JSON-RPC-Antwort: „“ bei Verwendung von infura

Mein Code:

const contract = require('truffle-contract');
const fs = require('fs');
const HDWalletProvider = require('truffle-hdwallet-provider');
const Web3 = require('web3');

const fileContents = fs.readFileSync('../../build/contracts/CoincodeToken.json', 'utf8');
const coincodeArtifacts = JSON.parse(fileContents);
const coincode = contract(coincodeArtifacts);

const walletMnemonic = 'god wwe lawsuit tiny mobile door raccoon chaos foil someone city siege';
const walletAPIUrl = 'https://rinkeby.infura.io/Fwp5nmX6Ze5FouVcBlHs';

const provider = new HDWalletProvider(walletMnemonic, walletAPIUrl);

const web3 = new Web3(provider);
coincode.setProvider(new Web3.providers.HttpProvider("https://rinkeby.infura.io/Fwp5nmX6Ze5FouVcBlHr"));

web3.eth.getAccounts(function (err, ac) {
    if (err != null) {
        console.error("There was an error fetching accounts.");
        return;
    }
    if (ac.length == 0) {
        console.error("Couldn't get any accounts! Make sure ethereum client is configured correctly.");
        return;
    }
    var accounts = ac;
    var account = accounts[0];
    web3.eth.defaultAccount = account;
    console.log(web3.eth.defaultAccount);

    coincode.deployed().then(function (instance) {
        return instance.transfer('0xa977575a23c55aaa992cfa585c2efc15b404259b', 2000000000000000000000, {from:account}).then(function (value) {
            value = value / 1000000000000000000;
            console.log("Printing value: " + value);
        });
    }).catch(function (e) {
        console.error(e);
    });
});

Ausgang:

0x24a60d3abe605a0ffc2852863eba5e517e5a4fc4

Error: Invalid JSON RPC response: ""
    at Object.InvalidResponse (/home/pravin-coincode/infura/node_modules/web3/lib/web3/errors.js:38:16)
    at XMLHttpRequest.request.onreadystatechange (/home/pravin-coincode/infura/node_modules/web3/lib/web3/httpprovider.js:125:24)
    at XMLHttpRequestEventTarget.dispatchEvent (/home/pravin-coincode/infura/node_modules/xhr2/lib/xhr2.js:64:18)
    at XMLHttpRequest._setReadyState (/home/pravin-coincode/infura/node_modules/xhr2/lib/xhr2.js:354:12)
    at XMLHttpRequest._onHttpResponseEnd (/home/pravin-coincode/infura/node_modules/xhr2/lib/xhr2.js:509:12)
    at IncomingMessage.<anonymous> (/home/pravin-coincode/infura/node_modules/xhr2/lib/xhr2.js:469:24)
    at IncomingMessage.emit (events.js:187:15)
    at endReadableNT (_stream_readable.js:1090:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)