Creating raw transactions for sending ERC721 tokens

Question

I was able to create raw transactions for eth following this article https://medium.com/blockchain-musings/how-to-create-raw-transactions-in-ethereum-part-1-1df91abdba7c

However, how can I create raw transactions when send ERC721 tokens? More specifically, where do I add the token id field when creating raw transactions?

Answer 1

A token transfer operation is actually a smart contract method call, which is a bit different than simple ETH sending:

• you'll have to fill the data: portion of the tx with the info related to the smart contract method call (more below)
• the from: address is the same as in a normal ETH send operation
• the to: address is the address of the smart contract, not the address of the recipient
• the value: field is 0

How to fill the data field. The example is done using web3js v1.0+. You'll need to have:

• your smart contract's ABI. Let's say you store that in variable ctrABI
• an instance of Web3. Let's say that's stored in variable web3

• the address where your ERC721 smart contract is deployed - ctrAddress

  const ctrInstance = new web3.eth.Contract(JSON.parse(ctrABI), ctrAddress)
  const dataField = await ctrInstance.methods.transfer(addrTo, tokenId ).encodeABI();
  

And then proceed to build your transaction:

const txParams = {
  nonce: '0x6', // Replace by nonce for your account on geth node
  gasPrice: '0x09184e72a000', 
  gasLimit: '0x30000', //modify accordingly
  to: ctrAddress, 
  data: dataField,
  value: '0x00'
};