OPTIONS net::ERR_CONNECTION_REFUSED...but server is working as intended?! react/express

Question

I see there are a lot of posts on this subject already, so I apologize if this is a repeat.

What is strange and possibly unique (I don't know) is that the server seems to be functioning and executing the API call properly.

I have a React front end with an Express backend being hosted on an AWS EC2 instance. As said above, when my front end makes an axios.post request, the server does everything it is supposed to, but I'm am returned two errors. One is

OPTIONS http://us-west-1.compute.amazonaws.com:3000 net::ERR_CONNECTION_REFUSED

The other is

Error: Network Error
at createError (createError.js:17)
at XMLHttpRequest.handleError (xhr.js:87)

React code is:

import React from "react";
import PaypalExpressBtn from "react-paypal-express-checkout";
import axios from "axios";

export default class Pay extends React.Component {

constructor(props) {
 super(props);
 this.state = {
  items: {}
  };
 }

  render() {
    const onSuccess = payment => {
      axios
        .post("http://compute.amazonaws.com:3000/", {
          value: this.props.value,
          fileName: this.props.fileName,
          hash: this.props.hash
        })
        .then(response => console.log(response.data))
        .catch(function(error) {
          console.log(error);
        });

      console.log(payment);
    };

    let env = "sandbox"; // you can set here to 'production' for production
    let currency = "USD"; // or you can set this value from your props or state
    let total = 3.33; // same as above, this is the total amount (based on 

    const client = {
      sandbox:
        "...key...",
      production: "YOUR-PRODUCTION-APP-ID"
    };

    return (
      <div>
        <PaypalExpressBtn
          onSuccess={onSuccess}
        />
      </div>
    );
  }
}

express code is:

const express = require("express");
const app = express();
const Tx = require("ethereumjs-tx");
var cors = require('cors')
const Web3 = require("web3");
const web3 = new Web3(
  "https://ropsten.infura.io/v3/d55489f8ea264a1484c293b05ed7eb85"
);

app.use(cors());

const abi = [...]

const contractAddress = "0x15E1ff7d97CB0D7C054D19bCF579e3147FC9009b";
const myAccount = "0x59f568176e21EF86017EfED3660625F4397A2ecE";
const privateKey1 = new Buffer(
  "...privateKey...",
  "hex"
);

app.post("/", function(req, res, next) {
 var hashValue = req.body.hash,
 fileName = req.body.fileName,
 value = req.body.value;

  const contract = new web3.eth.Contract(abi, contractAddress, {
    from: myAccount
    // gas: '50000'
  });

  web3.eth.getTransactionCount(myAccount, (err, txCount) => {
    //Smart contract data
    const data = contract.methods
      .setHashValue(value + " " + fileName + " " + hashValue)
      .encodeABI();

    // Build the transaction
    const txObject = {
      nonce: web3.utils.toHex(txCount),
      gasLimit: web3.utils.toHex(1000000),
      gasPrice: 20000000000,
      data: data,
      from: myAccount,
      to: contractAddress
    };

    // Sign the transaction
    const tx = new Tx(txObject);

    const serializedTx = tx.serialize();
    // const raw = '0x' + serializedTx.toString('hex')

    // Broadcast the transaction
    web3.eth
      .sendSignedTransaction("0x" + serializedTx.toString("hex"))
      .on("receipt", console.log);
    next();
  });
});

app.listen(3000, () => console.log("listening on 3000"));

I would reiterate that the server is broadcasting the Ethereum transaction as intended. The reason that I am asking is because I do not want errors, and am checking to see if this is part of a larger issue I'm having with a JSON return call.

Answer 1

I resolved this by adding a res.json()

web3.eth
  .sendSignedTransaction("0x" + serializedTx.toString("hex"))
  .on("receipt", console.log, res.json);