Smart contracts have revolutionized how digital agreements are executed in decentralized environments. Built on blockchain technology, these self-enforcing programs eliminate intermediaries and ensure trustless interactions. Solidity, the most widely used language for Ethereum-based smart contracts, empowers developers to create powerful decentralized applications (dApps). In this guide, we’ll walk through building a Solidity smart contract designed to send Binance Coin (BNB), manage gas fees, and deploy seamlessly on the Binance Smart Chain (BSC).
Whether you're new to blockchain development or expanding your dApp to multiple networks, understanding cross-chain deployment and gas handling is essential.
Understanding the Core Components of a BNB-Sending Smart Contract
To build a functional smart contract that transfers BNB, we start by leveraging the ERC-20 token standard, which defines a common set of rules for fungible tokens on Ethereum-compatible blockchains. Although BNB is native to BSC, its wrapped version on Ethereum follows the ERC-20 standard—making it compatible with standard token interfaces.
We begin by declaring the Solidity version and importing the IERC20 interface:
pragma solidity ^0.8.0;
interface IERC20 {
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
}This interface allows our contract to interact with the BNB token contract using transferFrom, enabling the movement of funds from one address to another—provided the sender has approved the transaction.
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Building the BNBSender Contract
Our smart contract, named BNBSender, includes state variables to store the sender, recipient, and transfer amount. These values are set during contract creation via the constructor.
contract BNBSender {
address public sender;
address public recipient;
uint256 public amount;
constructor(address _recipient, uint256 _amount) {
sender = msg.sender;
recipient = _recipient;
amount = _amount;
}The core functionality lies in the send() function, which executes the token transfer:
function send() external returns (bool) {
IERC20 BNB = IERC20(0xB8c77482e45F1F44dE1745F52C74426C631bDD52);
BNB.transferFrom(sender, recipient, amount);
return true;
}
}Here, we instantiate the BNB token contract using its known Ethereum address. When send() is called, it triggers transferFrom, moving the specified amount from the sender to the recipient.
Note: The sender must first approve this contract to spend their BNB tokens using an approve() call on the ERC-20 contract.Managing Gas Fees with Custom Modifiers
On any blockchain, transactions require gas to execute. While Ethereum uses ETH for gas, BSC uses BNB. To make our contract more robust, we can implement a custom modifier that enforces gas fee payments in BNB.
modifier paysGasFee() {
IERC20 BNB = IERC20(0xB8c77482e45F1F44dE1745F52C74426C631bDD52);
uint256 gasPrice = tx.gasprice;
uint256 gasUsed = 21000; // Standard gas for simple transfers
uint256 gasCost = gasPrice * gasUsed;
require(BNB.transferFrom(msg.sender, address(this), gasCost), "Gas fee payment failed");
_;
}By applying this modifier to the send() function:
function send() external paysGasFee returns (bool) {
IERC20 BNB = IERC20(0xB8c77482e45F1F44dE1745F52C74426C631bDD52);
BNB.transferFrom(sender, recipient, amount);
return true;
}We ensure users cover operational costs before their transaction proceeds. This pattern enhances sustainability, especially in multi-user dApps.
Frequently Asked Questions
Q: Can I use this contract directly on Binance Smart Chain?
A: Yes—but with adjustments. While the logic remains valid, you’ll need to update compiler settings and network configurations in your development environment (e.g., Remix IDE) to target BSC.
Q: Why does the contract use transferFrom instead of transfer?
A: transferFrom allows third-party execution. It’s ideal when a user approves a contract to move funds on their behalf, whereas transfer only moves tokens from the caller’s own balance.
Q: Is BNB an ERC-20 token on Ethereum?
A: Yes. The BNB you interact with on Ethereum is a wrapped version (WBNB or BEP-20-like), issued as an ERC-20 token with a fixed address.
Deploying Your Contract on Binance Smart Chain
Deploying on BSC offers lower fees and faster transactions compared to Ethereum. Follow these steps:
Configure MetaMask: Add the Binance Smart Chain network manually:
- Network Name: Binance Smart Chain
- RPC URL:
https://bsc-dataseed.binance.org/ - ChainID: 56
- Symbol: BNB
- Block Explorer:
https://bscscan.com
- Use Remix IDE: Paste your Solidity code into Remix, compile it using Solidity compiler v0.8.0+, and connect your MetaMask wallet.
- Deploy: Select “Injected Provider” as the environment, then click “Deploy.” Confirm the transaction in MetaMask.
Once deployed, you can interact with your contract directly through Remix or verify it on BscScan for transparency.
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Best Practices for Secure and Efficient Smart Contracts
When working with financial logic, security is paramount. Consider these tips:
- Use SafeMath libraries (though less critical in Solidity 0.8+ due to built-in overflow checks).
- Validate inputs using
require()statements. - Limit external calls to trusted contracts.
- Test thoroughly on testnets like BSC Testnet or Goerli before mainnet deployment.
- Audit your code or use automated tools like Slither or MythX.
Additionally, always simulate edge cases—such as zero addresses or insufficient balances—to prevent runtime errors.
Frequently Asked Questions
Q: What’s the difference between Ethereum and BSC when deploying contracts?
A: Both support EVM-compatible code, so Solidity contracts work on both. However, gas pricing and network speed differ significantly—BSC offers cheaper and faster transactions.
Q: How do I get test BNB for development?
A: Use the BSC Testnet Faucet to receive free test tokens for experimenting without financial risk.
Q: Can I upgrade this contract later?
A: By default, deployed contracts are immutable. For upgradable logic, explore proxy patterns like OpenZeppelin’s Transparent Proxy or UUPS.
Final Thoughts
Creating a Solidity smart contract to send BNB and manage gas fees is a foundational skill in blockchain development. With proper design patterns and attention to security, you can build scalable dApps that operate across chains like Ethereum and Binance Smart Chain.
As decentralized finance (DeFi) continues to grow, mastering these concepts positions developers at the forefront of innovation.
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Frequently Asked Questions
Q: Do I need to pay gas in ETH even when using BNB?
A: No. On Ethereum, gas is paid in ETH; on BSC, it’s paid in BNB. Ensure your wallet holds the correct native token for the network you’re using.
Q: Can one contract work on both Ethereum and BSC?
A: Yes. Since both are EVM-compatible, the same bytecode can be deployed on either chain—though token addresses may differ.
Q: How can I track my deployed contract?
A: Use block explorers: Etherscan for Ethereum and BscScan for Binance Smart Chain. Simply paste your contract address to view transactions and verify source code.
Core Keywords: Solidity smart contracts, sending BNB, Ethereum network, Binance Smart Chain, gas fees, ERC-20 standard, blockchain development, decentralized applications