Transaction Broadcasting

Overview

The OKX DEX SDK provides transaction broadcasting with built-in MEV (Maximal Extractable Value) protection. This feature helps protect your transactions from front-running and sandwich attacks.

API Whitelist Required: Transaction broadcasting requires your API key to be whitelisted. Contact OKX support to enable this feature.

Basic Transaction Broadcasting

Sign Your Transaction

First, create and sign your transaction:

import { OKXDexClient } from '@okxweb3/dex-sdk';
import { ethers } from 'ethers';
import { createEVMWallet } from '@okxweb3/dex-sdk';

const provider = new ethers.JsonRpcProvider(process.env.EVM_RPC_URL!);
const evmWallet = createEVMWallet(process.env.EVM_PRIVATE_KEY!, provider);

const client = new OKXDexClient({
  apiKey: process.env.OKX_API_KEY!,
  secretKey: process.env.OKX_SECRET_KEY!,
  apiPassphrase: process.env.OKX_API_PASSPHRASE!,
  projectId: process.env.OKX_PROJECT_ID!,
  evm: { wallet: evmWallet }
});

// Get swap data
const swapData = await client.dex.getSwapData({
  chainIndex: '8453',
  fromTokenAddress: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  toTokenAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
  amount: '3000000000000000', // 0.003 ETH
  slippagePercent: '0.05',
  userWalletAddress: evmWallet.address
});

const txData = swapData.data[0]?.tx;

// Sign the transaction
const nonce = await provider.getTransactionCount(evmWallet.address);
const transaction = {
  to: txData.to,
  value: txData.value,
  data: txData.data,
  gasLimit: txData.gas,
  maxFeePerGas: txData.maxFeePerGas,
  maxPriorityFeePerGas: txData.maxPriorityFeePerGas,
  nonce: nonce,
  chainId: 8453
};

const signedTx = await evmWallet.signTransaction(transaction);
console.log('Transaction signed');

Broadcast the Transaction

const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '8453',
  address: evmWallet.address,
  enableMevProtection: true  // Enable MEV protection
});

console.log('Transaction broadcasted!');
console.log('Order ID:', broadcastResult.data[0].orderId);
console.log('Transaction Hash:', broadcastResult.data[0].txHash);

MEV Protection

MEV protection helps prevent front-running and sandwich attacks by routing your transaction through protected channels.

Enabling MEV Protection

const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '8453',
  address: evmWallet.address,
  enableMevProtection: true  // Protects against MEV attacks
});

Without MEV Protection

const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '8453',
  address: evmWallet.address,
  enableMevProtection: false  // Standard public mempool
});

MEV Risk: Without MEV protection, your transaction is vulnerable to:

Front-running: Others see your transaction and submit a similar one with higher gas
Sandwich attacks: Attackers place trades before and after yours to profit from price movement
Slippage manipulation: Market makers exploit your slippage tolerance

Complete Broadcasting Example

import { OKXDexClient } from '@okxweb3/dex-sdk';
import { ethers } from 'ethers';
import { createEVMWallet } from '@okxweb3/dex-sdk';

const provider = new ethers.JsonRpcProvider(process.env.EVM_RPC_URL!);
const evmWallet = createEVMWallet(process.env.EVM_PRIVATE_KEY!, provider);

const client = new OKXDexClient({
  apiKey: process.env.OKX_API_KEY!,
  secretKey: process.env.OKX_SECRET_KEY!,
  apiPassphrase: process.env.OKX_API_PASSPHRASE!,
  projectId: process.env.OKX_PROJECT_ID!,
  evm: { wallet: evmWallet }
});

async function broadcastSwap() {
  try {
    console.log('=== Complete Swap Workflow with Broadcast ===');
    console.log('Wallet Address:', evmWallet.address);
    
    // Step 1: Get swap data
    console.log('\n1. Getting swap data...');
    const swapData = await client.dex.getSwapData({
      chainIndex: '8453',
      fromTokenAddress: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
      toTokenAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
      amount: '3000000000000000', // 0.003 ETH
      slippagePercent: '0.05',
      userWalletAddress: evmWallet.address
    });

    const txData = swapData.data[0]?.tx;
    if (!txData) {
      throw new Error('No transaction data received');
    }

    console.log('✅ Swap data received');
    console.log('- From amount:', swapData.data[0].routerResult.fromTokenAmount);
    console.log('- To amount:', swapData.data[0].routerResult.toTokenAmount);
    console.log('- Gas estimate:', txData.gas);

    // Step 2: Sign the transaction
    console.log('\n2. Signing transaction...');
    const nonce = await provider.getTransactionCount(evmWallet.address);
    
    const transaction = {
      to: txData.to,
      value: txData.value,
      data: txData.data,
      gasLimit: txData.gas,
      maxFeePerGas: txData.maxFeePerGas,
      maxPriorityFeePerGas: txData.maxPriorityFeePerGas,
      nonce: nonce,
      chainId: 8453
    };

    const signedTx = await evmWallet.signTransaction(transaction);
    console.log('✅ Transaction signed');

    // Step 3: Broadcast with MEV protection
    console.log('\n3. Broadcasting transaction with MEV protection...');
    const broadcastResult = await client.dex.broadcastTransaction({
      signedTx: signedTx,
      chainIndex: '8453',
      address: evmWallet.address,
      enableMevProtection: true
    });

    console.log('✅ Transaction broadcasted!');
    console.log('- Order ID:', broadcastResult.data[0].orderId);
    console.log('- Transaction Hash:', broadcastResult.data[0].txHash);
    console.log('- Explorer:', `https://web3.okx.com/explorer/base/tx/${broadcastResult.data[0].txHash}`);

    return {
      orderId: broadcastResult.data[0].orderId,
      txHash: broadcastResult.data[0].txHash
    };
  } catch (error) {
    console.error('Error in swap workflow:', error);
    throw error;
  }
}

broadcastSwap();

Solana: Jito MEV Protection

For Solana transactions, use Jito for MEV protection:

const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '501', // Solana
  address: solanaWallet.address,
  jitoSignedTx: jitoSignedTransaction  // Jito-signed transaction
});

Advanced Options

Custom Extra Data

Provide additional metadata with your transaction:

const extraData = {
  enableMevProtection: true,
  customField: 'value'
};

const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '8453',
  address: evmWallet.address,
  extraData: JSON.stringify(extraData)
});

Transaction Verification

After broadcasting, verify the transaction:

const { orderId, txHash } = broadcastResult.data[0];

// Track transaction status
const orders = await client.dex.getTransactionOrders({
  address: evmWallet.address,
  chainIndex: '8453',
  orderId: orderId
});

const order = orders.data[0]?.orders[0];
if (order) {
  console.log('Transaction status:', order.txStatus);
  console.log('Transaction hash:', order.txHash);
}

Error Handling

Handle Broadcast Failures

try {
  const broadcastResult = await client.dex.broadcastTransaction({
    signedTx: signedTx,
    chainIndex: '8453',
    address: evmWallet.address,
    enableMevProtection: true
  });
  
  console.log('Success:', broadcastResult.data[0].txHash);
} catch (error) {
  if (error instanceof Error) {
    if (error.message.includes('nonce')) {
      console.error('Nonce error - transaction may already be pending');
    } else if (error.message.includes('gas')) {
      console.error('Gas estimation error - increase gas limit');
    } else if (error.message.includes('whitelist')) {
      console.error('API key not whitelisted for broadcasting');
    } else {
      console.error('Broadcast failed:', error.message);
    }
  }
}

Retry Logic

async function broadcastWithRetry(params: any, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      const result = await client.dex.broadcastTransaction(params);
      return result;
    } catch (error) {
      console.log(`Attempt ${i + 1} failed, retrying...`);
      if (i === maxRetries - 1) throw error;
      await new Promise(resolve => setTimeout(resolve, 2000 * (i + 1)));
    }
  }
}

const result = await broadcastWithRetry({
  signedTx: signedTx,
  chainIndex: '8453',
  address: evmWallet.address,
  enableMevProtection: true
});

Best Practices

Always Use MEV Protection

For production applications, always enable MEV protection:

const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '8453',
  address: evmWallet.address,
  enableMevProtection: true  // Always true for production
});

Verify Network Connection

const network = await provider.getNetwork();
console.log('Connected to network:', network.name, 'Chain ID:', network.chainId);

if (network.chainId !== 8453) {
  throw new Error(`Wrong network. Expected Base (8453), got ${network.chainId}`);
}

Monitor Gas Prices

Check gas prices before broadcasting:

const gasPrice = await client.dex.getGasPrice('8453');
const currentGwei = Number(gasPrice.data[0].maxFeePerGas) / 1e9;

if (currentGwei > 50) {
  console.warn('High gas prices detected:', currentGwei, 'gwei');
  // Consider waiting or using a different chain
}

API Reference

broadcastTransaction

Parameters:

signedTx - Signed transaction hex string (required)
chainIndex - Chain identifier (required)
address - Wallet address (required)
enableMevProtection - Enable MEV protection (optional, recommended: true)
jitoSignedTx - Jito-signed transaction for Solana (optional)
extraData - Additional metadata as JSON string (optional)

Returns:

orderId - Unique order identifier for tracking
txHash - Transaction hash

Whitelist Requirement: This endpoint requires API key whitelisting. Contact OKX support to enable broadcasting for your API key.

Get Started

Core Concepts

Guides

Advanced Features

Transaction Broadcasting

Overview

Basic Transaction Broadcasting

MEV Protection

Enabling MEV Protection

Without MEV Protection

Complete Broadcasting Example

Solana: Jito MEV Protection

Advanced Options

Custom Extra Data

Transaction Verification

Error Handling

Handle Broadcast Failures

Retry Logic

Best Practices

Always Use MEV Protection

Verify Network Connection

Monitor Gas Prices

API Reference

broadcastTransaction

Next Steps

Order Tracking

Gas Estimation

Build docs developers (and LLMs) love

Get Started

Core Concepts

Guides

Advanced Features

​Overview

​Basic Transaction Broadcasting

​MEV Protection

​Enabling MEV Protection

​Without MEV Protection

​Complete Broadcasting Example

​Solana: Jito MEV Protection

​Advanced Options

​Custom Extra Data

​Transaction Verification

​Error Handling

​Handle Broadcast Failures

​Retry Logic

​Best Practices

​Always Use MEV Protection

​Verify Network Connection

​Monitor Gas Prices

​API Reference

​broadcastTransaction

​Next Steps

Order Tracking

Gas Estimation

Build docs developers (and LLMs) love

Overview

Basic Transaction Broadcasting

MEV Protection

Enabling MEV Protection

Without MEV Protection

Complete Broadcasting Example

Solana: Jito MEV Protection

Advanced Options

Custom Extra Data

Transaction Verification

Error Handling

Handle Broadcast Failures

Retry Logic

Best Practices

Always Use MEV Protection

Verify Network Connection

Monitor Gas Prices

API Reference

broadcastTransaction

Next Steps