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I have two Ethereum generated accounts I am managing and need to programmatically send tokens between the two accounts.

I've created two accounts and can send ERC20 tokens from a contract to an address but need to send from addresses to addresses. I am using the sample solidity token on the Ethereum website.

It has a function called transfer to send tokens between accounts:

function transfer(address _to, uint256 _value)

I need to now connect to this contract using web3, and then send a certain number of tokens generated to another account. I've been struggling with how to do this for quite some time and hoping this community could help. Here is what I have thus far, using web3 version 0.20.0:

const Web3 = require("web3");
const web3 = new Web3();
web3.setProvider(new 
web3.providers.HttpProvider("https://ropsten.infura.io/XXXXXX"));
var abi = [ {} ] // redacted on purpose
const account1 = "0x9..."
const account2 = "0x3..."
var count = web3.eth.getTransactionCount(account1);
var abiArray = abi;
var contractAddress = "0x2...";
var contract =  web3.eth.contract(abiArray).at(contractAddress);


var data = contract.transfer.getData(account2, 10000, {from: account1});
var gasPrice = web3.eth.gasPrice;
var gasLimit = 90000;

var rawTransaction = {
  "from": account1,
  "nonce": web3.toHex(count),
  "gasPrice": web3.toHex(gasPrice),
  "gasLimit": web3.toHex(gasLimit),
  "to": account2,
  "value": 0,
  "data": data,
  "chainId": 0x03
};

var privKey = new Buffer('XXXXXXXXXXXXXX', 'hex');
var tx = new Tx(rawTransaction);

tx.sign(privKey);
var serializedTx = tx.serialize();

web3.eth.sendRawTransaction('0x' + serializedTx.toString('hex'), function(err, hash) {
  if (!err)
      console.log(hash);
  else
      console.log(err);
});

This code however, does not transfer from one account to the other.

Code for Token Contract:

contract Token {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function Token(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != 0x0);
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value > balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` in behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }

    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     * @param _extraData some extra information to send to the approved contract
     */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, this, _extraData);
            return true;
        }
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other ccount
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);    // Check allowance
        balanceOf[_from] -= _value;                         // Subtract from the targeted balance
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
        totalSupply -= _value;                              // Update totalSupply
        Burn(_from, _value);
        return true;
    }
}
  • Did you check the transaction in etherscan, what is the transactions details in it? – Rajesh Oct 31 '17 at 4:35
  • @Rajesh here is the example transaction in etherscan, I tried sending a token but it does not send ropsten.etherscan.io/tx/… – Viper Oct 31 '17 at 4:43
  • Did you try this way? contract.transfer(account2, 10000, {from: account1}); – Rajesh Oct 31 '17 at 5:05
  • Refer to Send ERC20 token with web3 – Kris Roofe Apr 25 '18 at 10:27
3

You cannot send tokens directly from one address to another address. Tokens balances only exist in the Token contract storage. You necessarily have to send a transaction to the contract indicating you want to make a tranfer, so the contract can update the balances accordingly.

  • Is it possible to send transaction from contract to address? and then address to contract? I can send tokens from one address to another using myetherwallet or mist, why can't this be done with web3? – Viper Oct 31 '17 at 4:41
  • reddit.com/r/ethereum/comments/6sdgfv/… and ethereum.stackexchange.com/questions/28251/… say that any address can accept ERC20 tokens....am I missing something here? – Viper Oct 31 '17 at 4:45
  • Yes, you can 'send' tokens to any address. But to send tokens, you need to send a transaction to the token contract indicating you are transfering tokens. – Ismael Oct 31 '17 at 4:52
  • Do you have an example using web3 on how do do this? thank you – Viper Oct 31 '17 at 4:53
  • I think your example should work if you use "to": contractAddress, when building var rawTransaction. – Ismael Oct 31 '17 at 4:58
3

I give this example in geth console

    var theContract=eth.contract(THE_CONTRACT_ABI)
    var contractInstance = theContract.at(THE_CONTRACT_ADDRESS)
    personal.unlockAccount(YOUR_ACCOUNT_ADDRESS,YOUR_PASSWORD,100000)
    contractInstance.transfer(TO_THIS_ADDRESS,web3.toWei(20000),{from:YOUR_ACCOUNT_ADDRESS})
  • Thx, it works in geth console. > web3.version { api: "0.20.1", ethereum: "0x3f", network: "4", node: "Geth/v1.8.1-stable-1e67410e/darwin-amd64/go1.9.4", whisper: undefined, getEthereum: function(callback), getNetwork: function(callback), getNode: function(callback), getWhisper: function(callback) } – suiwenfeng Feb 24 '18 at 1:38
  • where does it dictate how many tokens are being sent? – JJacquet Jun 23 '18 at 1:44

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