Call deployed smart contract from node.js

Question

I have small test smart contract, which is deployed to my test network. And I want to use a server to call the function in the contract. Here is the code: payontime.sol

pragma solidity ^0.4.0;

contract payontime{
  address public remitter;
  address private remittee;
  uint value;
  bool public start;

  /*Only owner can use these function*/
  modifier onlyOwner(){
    if(msg.sender != remitter) throw;
    _;
  }

  /*Initialize the owner*/
  function payontime(address receiver) payable{
    remitter = msg.sender;
    value = msg.value;
    remittee = receiver;
    start = true;
    if(!remittee.send(value)){
        throw;
    }
  }

  function wakeUp() public returns (string){
    return "success" ; 
  }

  function getContractAddr() public returns(address){
    return this;
  }

  /*Get the remittee*/
  function getRemitee() public returns(address){
    return remittee;
  }
}

I use truffle serve and a webpage to new the contract.

app.js

import { default as Web3} from 'web3';
import { default as contract } from 'truffle-contract'
import payontime_artifacts from '../../build/contracts/payontime.json'
var payontime = contract(payontime_artifacts);

window.App = {
    sendCoin : function(){

        var sender = web3.eth.accounts[0];
        var receiver = document.getElementById('receiver').value;
        var amount =         parseInt(document.getElementById('amount').value);
    web3.eth.getBalance(receiver,function(error,result){
        if(!error){
            consol.log("Before transfer: " + result );
        }else{
            console.log("Error: " + error);
        }
    });

    var newContract = payontime.new(receiver,{from:sender, value:amount}).then(
        function(myPay){
            console.log(myPay.getContractAddr.call());
        }).then(
        function(){
            web3.eth.getBalance(receiver,function(error,result){
                if(!error){
                    console.log("After transfer: " + result );
                }else{
                    console.log("Error: " + error);
                }
            });
        });
    }
}

window.addEventListener('load', function() {
  // Checking if Web3 has been injected by the browser (Mist/MetaMask)
  if (typeof web3 !== 'undefined') {
    console.warn("Using web3 detected from external source. If you find that your accounts don't appear or you have 0 MetaCoin, ensure you've configured that source properly. If using MetaMask, see the following link. Feel free to delete this warning. :) http://truffleframework.com/tutorials/truffle-and-metamask")
    // Use Mist/MetaMask's provider
    window.web3 = new Web3(web3.currentProvider);
  } else {
    console.warn("No web3 detected. Falling back to http://localhost:8545. You should remove this fallback when you deploy live, as it's inherently insecure. Consider switching to Metamask for development. More info here: http://truffleframework.com/tutorials/truffle-and-metamask");
    // fallback - use your fallback strategy (local node / hosted node + in-dapp id mgmt / fail)
    window.web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
  }
  payontime.setProvider(web3.currentProvider);
});

app.js logs the address 0x1d379f2ab48ad20319e9f81cb45af415aa6f2966 , and I want to use this address to call the wakeUp() in the payontime.sol through another application index.js.

const Web3 = require('web3');

/* Connect to ethereum node */
const etherUrl = "http://localhost:8545";
const abi = [{"constant":false,"inputs":[],"name":"wakeUp","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"getContractAddr","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"remitter","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"start","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"getRemitee","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"inputs":[{"name":"receiver","type":"address"}],"payable":true,"type":"constructor"}];

let web3 = new Web3();
web3.setProvider(new web3.providers.HttpProvider(etherUrl));


/*Call the function which already deployed on ethereum network
  Notice: ABI have to modifeid when the smart contract code change*/
var contractInstance = web3.eth.contract(abi).at('0x1d379f2ab48ad20319e9f81cb45af415aa6f2966');
var reply = "false";
reply = contractInstance.wakeUp.call(function(error,result){
    if(error){
        console.log("Error");
        throw error;
    }else{
        return result;
    }
});
console.log(reply);

But there is an error message: BigNumber Error: new BigNumber() not a base 16 number I found it might be caused by not fully synced. I think it have some problem when I call the function in a deployed contract. So how can I call a deployed contract from web.js?

Zvezdomir Zlatinov Zvezdomir Zlatinov · Accepted Answer · 2017-04-06T08:00:11

contractInstance.wakeUp.call is calling the function as constant, but the function is not defined as constant:

function wakeUp() public returns (string){
    return "success" ; 
}

has to be:

function wakeUp() public constant returns (string){
    return "success" ; 
}

If your Solidity function doesn't change the blockchain state and is just reading data, you should define it as constant.

Call deployed smart contract from node.js

2 Answers