Ethereum (ETH) Exchange Wallet Development: ERC20 Token Detection

Understanding ERC20 Token Standards

The ERC20 token standard is a technical specification used for token implementation on the Ethereum blockchain. Below is the Solidity interface definition for ERC20 tokens:

pragma solidity ^0.4.24;

contract ERC20 {
    // Contract name e.g., Tether USD
    string public constant name = "";
    
    // Token symbol e.g., USDT
    string public constant symbol = "";
    
    // Decimal places e.g., 6
    uint8 public constant decimals = 0;
    
    // Returns total token supply
    function totalSupply() public constant returns (uint);
    
    // Returns token balance of specified address
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    
    // Returns approved spending allowance
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    
    // Transfers tokens to another address
    function transfer(address to, uint tokens) public returns (bool success);
    
    // Approves token spending by another address
    function function approve(address spender, uint tokens) public returns (bool success);
    
    // Transfers tokens from one address to another
    function transferFrom(address from, address to, uint tokens) public returns (bool success);
    
    // Transfer event notification
    event Transfer(address indexed from, address indexed to, uint tokens);
    
    // Approval event notification
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}

ERC20 ABI (Application Binary Interface)

The ABI defines how to interact with ERC20 contracts. Here's the standard JSON ABI:

[
    {
        "constant": true,
        "inputs": [],
        "name": "name",
        "outputs": [{"name": "", "type": "string"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    },
    // Additional functions omitted for brevity
    // Includes balanceOf, transfer, approve, etc.
    {
        "anonymous": false,
        "inputs": [
            {"indexed": true, "name": "from", "type": "address"},
            {"indexed": true, "name": "to", "type": "address"},
            {"indexed": false, "name": "tokens", "type": "uint256"}
        ],
        "name": "Transfer",
        "type": "event"
    }
]

Implementing ERC20 Detection in Go

Here's a Go implementation for detecting and interacting with ERC20 tokens:

package eth

import (
    "math/big"
    "strings"
    ethereum "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/accounts/abi"
    "github.com/ethereum/go-ethereum/accounts/abi/bind"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/event"
)

const EthABI = `[{"constant":true,"inputs":[],"name":"name"...}]`

// Eth represents an ERC20 token contract
type Eth struct {
    EthCaller      // Read-only binding
    EthTransactor  // Write-only binding
    EthFilterer    // Log filterer
}

// Filtering Transfer Events
type LogTransfer struct {
    From   string
    To     string
    Tokens *big.Int
}

func ParseTransferLog(contractAbi abi.ABI, log types.Log) (*LogTransfer, error) {
    var transferEvent LogTransfer
    err := contractAbi.Unpack(&transferEvent, "Transfer", log.Data)
    if err != nil {
        return nil, err
    }
    
    transferEvent.From = strings.ToLower(common.HexToAddress(log.Topics[1].Hex()).Hex())
    transferEvent.To = strings.ToLower(common.HexToAddress(log.Topics[2].Hex()).Hex())
    
    return &transferEvent, nil
}

Querying Blockchain Logs

To detect ERC20 token transactions, we query blockchain logs using eth_getLogs:

// FilterLogs executes a filter query
func (ec *Client) FilterLogs(ctx context.Context, q ethereum.FilterQuery) ([]types.Log, error) {
    var result []types.Log
    arg, err := toFilterArg(q)
    if err != nil {
        return nil, err
    }
    err = ec.c.CallContext(ctx, &result, "eth_getLogs", arg)
    return result, err
}

Filter Parameters

👉 Learn more about Ethereum token standards

FAQ Section

How do I detect if an address is an ERC20 token?

To detect ERC20 tokens:

1. Check if the address has bytecode
2. Verify it implements required ERC20 methods
3. Check for standard Transfer events

What's the difference between ERC20 and other token standards?

ERC20 is the basic fungible token standard. Other standards like ERC721 (NFTs) and ERC1155 (multi-token) offer different functionality for non-fungible or semi-fungible tokens.

How can I optimize ERC20 token detection?

Optimize by:

• Caching frequently accessed token contracts
• Using bulk RPC requests
• Implementing background detection processes

👉 Advanced Ethereum development techniques

Best Practices for Token Detection

1. Error Handling: Always handle cases where contracts don't fully comply with standards
2. Batch Processing: Process multiple token checks in single RPC calls when possible
3. Event Monitoring: Set up persistent connections for real-time event monitoring