实现 ERC20 和 Ether 转账监听

实现ERC20 和 Ether 转账监听

ERC20 转账监听

• 所需环境和工具

  1. geth 全节点
  2. web3

• 对 ERC20 的转账监听有如下两个方案

  1. 将块高作为参数，调用 eth_getLogs 来获取 ERC20 的转账事件
  2. 使用 web3.eth.subscribe("logs") 实时监听 ERC20 转账事件

如下提供第一种方案。

const Web3 = require('web3');
const Decimal = require('decimal.js');
const abiDecoder = require('abi-decoder');

const YOUR_ALCHEMYAPI_API_KEY = 'YOUR_API_KEY';

const EVENT_TRANSFER = '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef';
const ERC20_TRANSFER_EVENT_ABI = [{
    "anonymous": false,
    "inputs": [
        {
            "indexed": true,
            "name": "src",
            "type": "address"
        },
        {
            "indexed": true,
            "name": "dst",
            "type": "address"
        },
        {
            "indexed": false,
            "name": "wad",
            "type": "uint256"
        }
    ],
    "name": "Transfer",
    "type": "event"
}];
abiDecoder.addABI(ERC20_TRANSFER_EVENT_ABI);

const web3 = new Web3(`wss://eth-mainnet.ws.alchemyapi.io/v2/${YOUR_ALCHEMYAPI_API_KEY}`);

/**
 * 取出当前区块上所有的 ERC20 转账事件
 * @param number
 * @returns {Promise.}
 */
async function getErc20TransfersByBlock(number) {
    const number = 1000000;
    const blockLogs = await web3.eth.getPastLogs({
        fromBlock: number,
        toBlock: number,
        address: null,
        topics: [EVENT_TRANSFER]
    });

    const transfers = [];
    for (const log of blockLogs) {
        // todo get erc20 decimals
        const DECIMALS_OF_ERC20 = null;
        const decodeData = abiDecoder.decodeLogs([log])[0];
        const from = decodeData.events[0].value;
        const to = decodeData.events[1].value;
        const raw_value = new Decimal(decodeData.events[2].value);
        const decimal = Decimal.pow(10, DECIMALS_OF_ERC20);
        const value = raw_value.div(decimal);
        console.debug(`from=${from} to=${to} value=${value} contract=${log.address}`);
        transfers.push({from, to, value, contract: log.address});
    }
    return transfers;
}

(async () => {
    while (true) {
        const latest = await this.web3.eth.getBlock('latest', true);
        const transfers = await getErc20TransfersByBlock(latest);
        // ...
    }
})();

• YOUR_ALCHEMYAPI_API_KEY : https://alchemyapi.io 是一个提供在线 geth 的平台，你可以通过注册获取到 KEY 连接 geth。自建 geth 节点需要支付相当的成本，尤其是 geth 的归档全节点，硬盘容量需要 6TB 以上（截止 2021年3月）。
• DECIMALS_OF_ERC20 : ERC20 代币的小数位数，可以自己维护在数据库，也可以实时从链上调用获取。

Ether 转账监听

• 所需环境和工具
  1. geth 归档全节点
  2. web3

Ether 转账有四类，一种是 external transaction，也就是普通的 Ether 转账。另外一种是 internal transaction，是通过智能合约进行的 Ether 转账。internal transaction 需要通过调用 debug 或者 trace 模块来获取合约执行的详细过程。剩余两类：coinbase 挖矿奖励和 selfdestruct 合约自毁。

特别注意，如果想要在自己的 geth 或者 openethereum 节点上调用 debug 、 trace 模块，必须将节点设置为 归档全节点 模式，即 syncmode=full 和 gcmode=archive。归档全节点需要至少 6TB 的磁盘空间（截止2021年3月）。

获取 internal transaction 需要归档全节点，可以考虑使用 infura.io 或者 alchemyapi.io ，支付较少的成本即可获取归档全节点的全部能力。

如下是通过 openethereum 的 trace_transaction 来获取 internal transaction 的例子。

const YOUR_ALCHEMYAPI_API_KEY = 'YOUR_API_KEY';
const web3 = new Web3(`wss://eth-mainnet.ws.alchemyapi.io/v2/${YOUR_ALCHEMYAPI_API_KEY}`);

web3.currentProvider.send({
        method: "trace_transaction",
        params: ['0x42b6ab2be4975708f70575fc7953d11692c84a4a19c5c8eec65c582870a4e85e', {
            disableStack: true,
            disableMemory: true,
            disableStorage: true
        }],
        jsonrpc: "2.0",
        id: "2"
    }, (err, res) => {
        console.info(`${JSON.stringify(res)}`);
    });

返回结果如下（部分），其中 action.value 大于 0 即可认为是 from 到 to 转账的 Ether 金额。

调用 debug_traceTransaction 前，必须确认 receipt.status 为 true

{
  "jsonrpc": "2.0",
  "result": [
    {
      "action": {
        "callType": "call",
        "from": "0xc1563bdf57bdb990c89070aa72cda57fe8d6913d",
        "gas": "0x5f2ad",
        "input": "0x36118b52ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff000000000000000000000000c1563bdf57bdb990c89070aa72cda57fe8d6913d",
        "to": "0xdcd33426ba191383f1c9b431a342498fdac73488",
        "value": "0x0"
      },
      "blockHash": "0x197f158db6b8263e7d518a4f8f5f43d689e76ca1921882dae75c4fc050b593d6",
      "blockNumber": 11962253,
      "result": {
        "gasUsed": "0x557e2",
        "output": "0x"
      },
      "subtraces": 5,
      "traceAddress": [],
      "transactionHash": "0xffdb1a501fdc51cc308cec9f60cadc6453b221ceec352b804b981da25814f1b9",
      "transactionPosition": 124,
      "type": "call"
    },
    {
      "action": {
        "callType": "staticcall",
        "from": "0xdcd33426ba191383f1c9b431a342498fdac73488",
        "gas": "0x5d382",
        "input": "0x70a08231000000000000000000000000c1563bdf57bdb990c89070aa72cda57fe8d6913d",
        "to": "0x030ba81f1c18d280636f32af80b9aad02cf0854e",
        "value": "0x0"
      },
      "blockHash": "0x197f158db6b8263e7d518a4f8f5f43d689e76ca1921882dae75c4fc050b593d6",
      "blockNumber": 11962253,
      "result": {
        "gasUsed": "0x2a3d",
        "output": "0x0000000000000000000000000000000000000000000000003782db004aad38f2"
      },
      "subtraces": 1,
      "traceAddress": [
        0
      ],
      "transactionHash": "0xffdb1a501fdc51cc308cec9f60cadc6453b221ceec352b804b981da25814f1b9",
      "transactionPosition": 124,
      "type": "call"
    }
  ],
  "id": 0
}