How to Build a Sniping Bot 🤖 with ethers-kt: Step-by-Step Guide for Beginners
Building a trading bot offers a compelling advantage in today’s trading environment, where 60–70% of trading activities are driven by algorithms.
This step-by-step guide aims to introduce beginners to the process of developing a sniping bot designed to operate on Ethereum and other EVM-compatible chains from scratch. Such bots are engineered to swiftly identify and execute trades, often during initial coin offerings or when new tokens are listed, ensuring the bot user gets the best possible entry price. By the end of this guide, you should have a basic yet functional sniping bot ready to deploy on any EVM-compatible chain, leveraging the speed and efficiency of algorithmic trading to your advantage.
Prerequisites
Before diving into the construction of a sniping bot on EVM-compatible chains, it is essential to prepare by gathering the right tools and familiarizing yourself with certain technologies. This section will outline all necessary prerequisites needed to follow along with this tutorial effectively.
Programming Language: Kotlin
Kotlin will be our primary programming language. Chosen for its conciseness, type safety, and speed, Kotlin significantly enhances the development process. It integrates seamlessly with Java, allowing us to leverage vast ecosystems of libraries and frameworks, including Spring Boot, which we will utilize for creating our bot. Kotlin’s expressive syntax and strong type inference reduce common programming errors, making it an ideal choice for developing robust and maintainable applications.
Framework: Spring Boot
Spring Boot is a powerful framework that simplifies the development of new Spring applications through convention over configuration. It is particularly useful for creating stand-alone, production-grade applications that you can “just run.”
Library: ethers-kt
Features:
- Intuitive, extensible and easy to use abstractions.
- Complete and type-safe smart contract binding generation from JSON-ABI files.
- Safe RPC error handling without throwing an exception.
- Async RPC requests by default.
- Batch RPC calls.
Basic Knowledge
To follow this tutorial you don’t need to know all of the above mentioned tools and libraries. However, basic programming skills as well understanding of blockchain concepts such as transactions, blocks, and smart contracts is essential.
Set up your environment
Create the Spring Boot Project
Since code is open sourced you can simply clone the open-source repository we have prepared. Alternatively you can set up Spring Boot project yourself by following this tutorial: https://spring.io/quickstart
- IntelliJ IDEA
- Kotlin and Gradle (Maven works too)
- Java 19 or higher
- Add Spring Web dependency
- Jar packaging
Import ethers-kt library
You’ll find detailed instructions here in the README.md file under the section Quickstart. First open the build.gradle.kts or pom.xml file located at the root of your project and follow the guidelines on adding plugins and dependencies, as illustrated in the included picture.
Implement bot logic
In this section, we’ll explore a strategy designed to interact with Ethereum’s Uniswap V2 protocol. This example utilizes the ethers-kt library to showcase real-time interaction with smart contracts, focusing on trading logic and event monitoring. The library also automatically generates smart contract wrappers in Kotlin from provided ABI files.
Overview of the EthersKtSniperBotStrategy Class
The EthersKtSniperBotStrategy class is a crucial part of our application, designed to demonstrate the programmatic interaction with Ethereum smart contracts, particularly for observing and executing transactions on the Uniswap V2 decentralized exchange..
Key Functionalities
- Event Subscription: The strategy begins by subscribing to the PairCreated events emitted from the Uniswap V2 Factory smart contract. This is crucial for the bot as it allows real-time detection of new trading pairs.
- Event Handling: Upon detecting a new pair, the strategy evaluates if the pair includes WETH (Wrapped Ether) and checks whether liquidity (reserves) is above zero. If there is no liquidity, we cannot make any trades.
- Transaction Execution: If the criteria are met, the bot initiates a swap transaction attempting to trade ETH for the other token in the newly created pair.
Detailed Breakdown
Initialization and Configuration:
A Provider object is created from HTTP/WS URL to interact with the Ethereum blockchain. A PrivateKeySigner is used for signing transactions. Config for both is provided via env variables.
Starting the Strategy
- When started, the strategy sets up a subscription to listen for PairCreated events using a UniswapV2Factory.PairCreated event filter.
- The subscription may fallback to polling if WebSocket subscriptions are unsupported. Note that this will use more RPC quotas if using paid providers such as Alchemy or Infura.
Handling New Pairs and Trading
- For each new pair, check if the pair’s reserves are non-zero and if one of the tokens is ETH. Strategy swaps native ETH for the other token via router, and we cannot swap if there is no liquidity in the pool.
- If both checks pass we send a transaction on chain.
Conclusion
This Kotlin and Spring Boot implementation not only serves as a practical guide to using the ethers-kt library but also as a foundation for readers to develop more sophisticated trading bots tailored to their specifications and risk profiles. Further enhancements could include integrating more complex trading strategies, better error handling, and adapting to multi-token scenarios. In the further tutorials we’ll dive deeper into the capabilities of ethers-kt, like streaming mempool transactions, simulating transactions and more so stay tuned. If you wish to discuss anything with us feel free to visit Kriptal.io where we develop software solutions and offer consulting and auditing services.
Before you go …
