Blockchain Server in Swift

A lightweight blockchain implementation written in Swift using the Vapor framework. This project demonstrates the core concepts of blockchain technology including mining, transactions, and consensus mechanisms.

Overview

This repository implements a blockchain with the following features:

• Proof of Work algorithm
• Transaction validation
• Consensus mechanism for distributed nodes
• RESTful API for interaction

This implementation is inspired by the concepts outlined in the article Learn Blockchains by Building One by Daniel van Flymen, adapted to Swift and the Vapor framework.

Requirements

• Swift 5.8+
• macOS or Linux

Getting Started

Build the Project

swift build

Run the Server

swift run

The blockchain server will start on port 8080 by default.

API Usage

You can interact with the blockchain API using cURL, Postman, or any HTTP client.

View the Blockchain

curl http://localhost:8080/chain

Mine a New Block

curl http://localhost:8080/mine

Create a New Transaction

curl -X POST -H "Content-Type: application/json" -d '{
    "sender": "sender-address",
    "recipient": "recipient-address",
    "amount": 5
}' http://localhost:8080/transactions/new

Register New Nodes

curl -X POST -H "Content-Type: application/json" -d '{
    "nodes": ["http://localhost:8081"]
}' http://localhost:8080/nodes/register

Resolve Consensus Issues

curl http://localhost:8080/nodes/resolve

Testing Multiple Nodes

To test the consensus mechanism, you need to run multiple nodes on different ports:

Configure and Run a Second Node

Modify the port configuration in configure.swift for the second node:

// In the second node's configure.swift
app.http.server.configuration.port = 8081

Run the second node:

swift run --working-directory /path/to/second/node

Register Nodes with Each Other

Register the second node with the first node:

curl -X POST -H "Content-Type: application/json" -d '{
    "nodes": ["http://localhost:8081"]
}' http://localhost:8080/nodes/register

Register the first node with the second node:

curl -X POST -H "Content-Type: application/json" -d '{
    "nodes": ["http://localhost:8080"]
}' http://localhost:8081/nodes/register

Test Consensus

Mine a few blocks on the first node:

curl http://localhost:8080/mine
curl http://localhost:8080/mine

Then invoke the consensus mechanism on the second node:

curl http://localhost:8081/nodes/resolve

This will synchronize node 2 with node 1, accepting the longer chain from node 1.

Contact

Author: Bo-Hsun Hsu Email: bohsunhsu@gmail.com

License

This project is available under the MIT License.