Creating a local blockchain

Oct 13, 2025 by wbrum.org 61 views

Introduction

In the world of blockchain development, testing and debugging are crucial steps in ensuring the smooth operation of your application. Ethereumjs/testrpc is a popular testing environment for Ethereum that allows developers to create a local blockchain for testing purposes. However, running it from a Docker container can be a bit tricky. In this article, we will explore how to run ethereumjs/testrpc from a Docker container and create a setup with another Docker container running an Express app.

What is Ethereumjs/Testrpc?

Ethereumjs/testrpc is a testing environment for Ethereum that allows developers to create a local blockchain for testing purposes. It provides a simple way to create a blockchain, deploy contracts, and interact with them. Ethereumjs/testrpc is built on top of the Ethereumjs library and provides a lot of features out of the box, such as:

Creating a local blockchain: Ethereumjs/testrpc allows you to create a local blockchain for testing purposes.
Deploying contracts: You can deploy contracts to the local blockchain using ethereumjs/testrpc.
Interacting with contracts: Ethereumjs/testrpc provides a simple way to interact with contracts on the local blockchain.

Why Run Ethereumjs/Testrpc from a Docker Container?

Running ethereumjs/testrpc from a Docker container provides several benefits, including:

Isolation: Running ethereumjs/testrpc from a Docker container provides isolation from the host system, which means that you can run multiple instances of ethereumjs/testrpc without worrying about conflicts.
Portability: Docker containers are portable, which means that you can run ethereumjs/testrpc on any system that has Docker installed, without worrying about dependencies or configuration.
Reusability: Docker containers are reusable, which means that you can use the same container for multiple projects, without having to recreate it each time.

Setting Up the Docker Environment

To run ethereumjs/testrpc from a Docker container, you will need to set up a Docker environment on your system. Here are the steps to follow:

Step 1: Install Docker

To install Docker, follow these steps:

Ubuntu/Debian: sudo apt-get update && sudo apt-get install docker.io
Red Hat/Fedora: sudo yum install docker
Mac: Install Docker Desktop from the official Docker website.

Step 2: Create a Dockerfile

To create a Docker container for ethereumjs/testrpc, you will need to create a Dockerfile. Here is an example Dockerfile that you can use:

FROM node:14 WORKDIR /app COPY package*.json ./ RUN npm install COPY . . EXPOSE 8545

CMD ["node", "testrpc.js"]

This Dockerfile uses the official Node.js 14 image as the base image and sets the working directory to /app. It then copies the package.json file and installs the dependencies using npm install. Finally, it copies the rest of the application code and exposes port 8545.

Step 3: Build the Docker Image

To build the Docker image, run the following command:

docker build -t ethereumjs/testrpc .

This command builds the Docker image with the name ethereumjs/testrpc.

Step 4: Run the Docker Container

To run the Docker container, run the following command:

docker run -p 8545:8545 ethereumjs/testrpc

This command runs the Docker container and maps port 8545 on the host system to port 8545 in the container.

Creating an Express App

To create an Express app that interacts with the ethereumjs/testrpc server, you will need to create a new Node.js project and install the required dependencies. Here are the steps to follow:

Step 1: Create a New Node.js Project

To create a new Node.js project, run the following command:

npm init -y

This command creates a new package.json file with the default values.

Step 2: Install the Required Dependencies

To install the required dependencies, run the following command:

npm install express

This command installs the Express.js framework.

Step 3: Create the Express App

To create the Express app, create a new file called app.js and add the following code:

const express = require('express');
const app = express();
app.get('/', (req, res) => {
res.send('Hello World!');
});
app.listen(3000, () => {
console.log('Server listening on port 3000');
});

This code creates an Express app that listens on port 3000 and responds with "Hello World!" when a GET request is made to the root URL.

Step 4: Run the Express App

To run the Express app, run the following command:

node app.js

This command runs the Express app.

Interacting with the Ethereumjs/Testrpc Server

To interact with the ethereumjs/testrpc server, you will need to use the web3 library. Here are the steps to follow:

Step 1: Install the Web3 Library

To install the web3 library, run the following command:

npm install web3

This command installs the web3 library.

Step 2: Create a Web3 Instance

To create a web3 instance, create a new file called index.js and add the following code:

const Web3 = require('web3');
const web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'));
console.log(web3.eth.accounts);

This code creates a web3 instance that connects to the ethereumjs/testrpc server on port 8545.

Step 3: Interact with the Ethereumjs/Testrpc Server

To interact with the ethereumjs/testrpc server, you can use the web3 instance to call methods on the contracts. Here is an example:

const contract = new web3.eth.Contract(abi, '0x...');
contract.methods.someMethod().call().then((result) => {
console.log(result);
});

This code calls the someMethod method on the contract and logs the result to the console.

Conclusion

Q: What is the purpose of running ethereumjs/testrpc from a Docker container?

A: Running ethereumjs/testrpc from a Docker container provides several benefits, including isolation, portability, and reusability. It allows you to create a local blockchain for testing purposes, deploy contracts, and interact with them in a controlled environment.

Q: How do I install Docker on my system?

A: To install Docker on your system, follow these steps:

Ubuntu/Debian: sudo apt-get update && sudo apt-get install docker.io
Red Hat/Fedora: sudo yum install docker
Mac: Install Docker Desktop from the official Docker website.

Q: How do I create a Dockerfile for ethereumjs/testrpc?

A: To create a Dockerfile for ethereumjs/testrpc, follow these steps:

Create a new file called Dockerfile in the root directory of your project.
Add the following code to the Dockerfile:

FROM node:14 WORKDIR /app COPY package*.json ./ RUN npm install COPY . . EXPOSE 8545

CMD ["node", "testrpc.js"]

Build the Docker image by running the command docker build -t ethereumjs/testrpc .

Q: How do I run the ethereumjs/testrpc server from a Docker container?

A: To run the ethereumjs/testrpc server from a Docker container, follow these steps:

Run the command docker run -p 8545:8545 ethereumjs/testrpc to start the container.
The container will start the testrpc server on port 8545.

Q: How do I interact with the ethereumjs/testrpc server using the web3 library?

A: To interact with the ethereumjs/testrpc server using the web3 library, follow these steps:

Install the web3 library by running the command npm install web3.
Create a new file called index.js and add the following code:

const Web3 = require('web3');
const web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'));
console.log(web3.eth.accounts);

Run the command node index.js to start the web3 instance.
You can now use the web3 instance to call methods on the contracts.

Q: What are some common issues that I may encounter when running ethereumjs/testrpc from a Docker container?

A: Some common issues that you may encounter when running ethereumjs/testrpc from a Docker container include:

Port conflicts: If you are running multiple containers on the same host, you may encounter port conflicts.
Network issues: If you are running the container on a network that has firewall rules or other network restrictions, you may encounter issues connecting to the container.
Docker version issues: If you are running an older version of Docker, you may encounter issues with the container.

Q: How do I troubleshoot issues with running ethereumjs/testrpc from a Docker container?

A: To troubleshoot issues with running ethereumjs/testrpc from a Docker container, follow these steps:

Check the Docker logs for any errors or warnings.
Check the container's network configuration to ensure that it is properly configured.
Check the container's port configuration to ensure that it is properly configured.
Try running the container in debug mode to get more detailed output.

Q: Can I use ethereumjs/testrpc with other blockchain frameworks?

A: Yes, you can use ethereumjs/testrpc with other blockchain frameworks. However, you will need to modify the Dockerfile and the web3 instance to accommodate the specific requirements of the other framework.

Q: Is ethereumjs/testrpc suitable for production use?

A: No, ethereumjs/testrpc is not suitable for production use. It is intended for testing and development purposes only. For production use, you should use a more robust and secure blockchain framework.