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How to authenticate and send contract method using web3.js 1.0

rated 0 times [ 33] [ 5] / answers: 1 / hits: 16076 / 7 Years ago, fri, october 6, 2017, 12:00:00

I am confused about how I should be executing a contract's method using the web3 1.0 library.

This code works (so long as I manually unlock the account first):

var contract = new web3.eth.Contract(contractJson, contractAddress);

contract.methods

  .transfer(0x0e0479bC23a96F6d701D003c5F004Bb0f28e773C, 1000)

  .send({

    from: 0x2EBd0A4729129b45b23aAd4656b98026cf67650A

  })

  .on('confirmation', (confirmationNumber, receipt) => {

    io.emit('confirmation', confirmationNumber);

  });

I get this error (if I don't unlock manually first):

Returned error: authentication needed: password or unlock

The above code is an API endpoint in node.js, so I want it to unlock or authenticate programmatically.

There is no method in web3.js 1.0 to unlock the account.

I also don't think this is necessary (at least that's what I am confused about). Since I am managing accounts, I know what the private key is.

I am thinking the transaction needs to be signed with the private key?? Is this correct? Is this effectively the same thing as unlocking the account?

I tried doing this:

var contract = new web3.eth.Contract(contractJson, contractAddress);



var tx = {

  from: ...{fromAddress -- address that has the private key below},

  to: ...,

  value: ...

};



var signed = web3.eth.accounts.signTransaction(tx, 

  ...{privateKey});



console.log(signed);



var promise = web3.eth.sendSignedTransaction(signed);

I get this error:

Returned error: The method net_version does not exist/is not available

What is the easiest way to authenticate and submit a transaction?

Ideally, I want to use the first approach in my code sample, as it is the cleanest.

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billtreytonb

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3 Years ago

answered 7 Years ago raveno · Accepted Answer

This code allows me to sign a transaction server-side (node.js) using the privateKey from the account I created (using web3.eth.accounts.create()), and send the signed transaction to the network without having to unlock the account.

I am using Geth 1.7.1

  var contract = new web3.eth.Contract(contractJson, contractAddress);

  var transfer = contract.methods.transfer(0x..., 490);

  var encodedABI = transfer.encodeABI();



  var tx = {

    from: 0x...,

    to: contractAddress,

    gas: 2000000,

    data: encodedABI

  }; 



  web3.eth.accounts.signTransaction(tx, privateKey).then(signed => {

    var tran = web3.eth.sendSignedTransaction(signed.rawTransaction);



    tran.on('confirmation', (confirmationNumber, receipt) => {

      console.log('confirmation: ' + confirmationNumber);

    });



    tran.on('transactionHash', hash => {

      console.log('hash');

      console.log(hash);

    });



    tran.on('receipt', receipt => {

      console.log('reciept');

      console.log(receipt);

    });



    tran.on('error', console.error);

  });