⚙️ How It Works (Solana Sandwich Bot ‐ Node.js) - cryptoking-max/solana-sandwich-bot GitHub Wiki

⚙️ How It Works (Solana Sandwich Bot - Node.js)

A sandwich attack involves inserting two trades around a target (victim) transaction to exploit price movements caused by that transaction. The attack is performed in this sequence:

[Front-run (you)] ➝ [Victim Trade] ➝ [Back-run (you)]

Let’s break this down step-by-step for Solana:

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1. Mempool Listening

• The bot connects to a private RPC node or gRPC stream (like Helius or Triton).
• It listens to pending swap instructions, especially targeting DEX aggregator transactions (e.g., Jupiter).
• Node.js tools: Use WebSocket (websocket, ws) or gRPC (@grpc/grpc-js) to subscribe to transaction data.

You listen for Swap, Route, or Jupiter-specific instructions in transactions before they're confirmed.

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2. Transaction Filtering

• The bot analyzes each transaction to:

  • Detect large swap amounts (e.g., >1000 USDC).
  • Ensure low slippage protection (i.e., sandwichable).
  • Confirm DEX involvement (usually Jupiter Aggregator).
  • Validate that the token pair has sufficient liquidity.

You decode instructions using @solana/web3.js or a parser like borsh or buffer-layout.

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3. Simulate Front-Run

• Before acting, the bot queries the Jupiter Quote API to simulate:

  • A small front-run buy of the same token pair.
  • The expected price impact of the victim’s trade.
  • The back-run sell profitability.

const res = await axios.get(`https://quote-api.jup.ag/v6/quote`, {
  params: {
    inputMint: SOL,
    outputMint: targetToken,
    amount: frontRunAmount,
    slippage: 0.5
  }
});

The goal is to ensure the round-trip trade will be profitable after the victim moves the price.

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4. Front-Run Execution

• The bot submits a buy transaction just before the victim’s transaction.
• This can be done by manually setting transaction priority or using Solana’s compute unit price to speed up confirmation.
• Use sendTransaction() with manual signing and pre-flight disabled for speed.

const transaction = new Transaction().add(...);
transaction.feePayer = yourPublicKey;
transaction.recentBlockhash = await getLatestBlockhash();
transaction.sign(...);
await connection.sendRawTransaction(serializedTx, { skipPreflight: true });

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5. Victim Transaction Monitoring

• The bot monitors the targeted transaction hash until it’s confirmed.
• Once confirmed, it ensures the price has moved in the predicted direction (in your favor).

This can be done using connection.getSignatureStatus() or listening for block confirmations.

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6. Back-Run Execution

• Once the price is favorable, the bot sends a sell transaction to complete the sandwich.
• It uses a Jupiter route or DEX swap back to the base token (e.g., USDC or SOL).
• The spread between buy and sell becomes the profit.

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7. Profit Tracking and Logs

• The bot calculates:

  • Entry price, exit price
  • Gas cost (compute unit cost × price)
  • Net profit in SOL or USDC

• Logs are stored locally or in a database (e.g., MongoDB or JSON logs).

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🔄 Summary Flow:

[Listen] ---> [Filter] ---> [Simulate] ---> [Front-Run]
                                      |
                             [Wait for Victim Confirm]
                                      |
                                [Back-Run Sell]
                                      |
                                [Log Profit / Loss]

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