A brutally simple blockchain written in Javascript ES6 and Node.js.
To develop a proof-of-work cryptocurrency in different steps with an educational purpose.
I start developing the minimum possible implementation of a blockchain.
Each attempt will include more functionalities so that the developer/student/aficionado can learn step by step how a blockchain works.
Let's define a blockchain as a digital record of messages kept in a P2P network. The name comes from its structure, in which individual records, called blocks, are linked together in single list, called a chain.
This first implementation attempt honors the minimum possible implementation of the definition above. I have decided to keep the code in a file (less than 200 lines) to show how easy to implement and compact it can be.
Let's start by listing the limitations of this first approach:
- It assumes all nodes are honest. Thus, there is no need for proof of work.
- It's not a cryptocurrency blockchain. The blockchain consists of a chain of blocks where each block contains only a single message (a string).
- Blocks are not created on a time base (as in 10 minutes per block in Bitcoin). Instead, one block is produced (mined) per each message received.
- Nodes propagate all the blocks (beginning from the genesis block) once they receive a new message. There is no mechanism that allows partial blockchains to be sent or retrieved.
- Full P2P implementation using TCP sockets. Nodes connect to each other to announce themselves and ping each other regularly to show they are still available.
- Nodes keep the longest chain as the valid chain.
- A simple HTTP server is also provided so that a client (a wallet) can send a message to any node of the blockchain.
- The HTTP server also can also be used as a very simple block explorer.
git clone https://github.com/landabaso/brutalchain.git
cd brutalchain
npm install
Create 3 nodes on your computer and send some messages to the blockchain:
npm run testHonestNodesOneMessagePerBlock
Some messages are automatically sent to the blockchain when running npm run testHonestNodesOneMessagePerBlock. You can also send your own messages anytime:
curl -H "Content-type:application/json" --data '{"message" : "My new message"}' http://localhost:20003/produceBlock
Close some of the clients and see how the list of peers on each node are automatically updated:
ps aux | grep 1-HonestNodesOneMessagePerBlock
kill [PUT HERE A PID]
You can also launch more nodes and see how they are added to the P2P network. First choose an available port HTTP_PORT for the HTTP server so that a client (a wallet) can connect to produce (mine) a message. Then set an available port P2P_PORT for the P2P socket. Finally, you must seed the socket address REMOTE_PEERS of an existing node (if available).
Note that REMOTE_PEERS can also be a comma separated list of addresses as in: REMOTE_PEERS=localhost:10001,localhost:10002.
However, a single node address is fine as seed since addresses automatically propagate through the network.
Taking all together, this is how you could start a new node:
HTTP_PORT=20004 P2P_PORT=10004 REMOTE_PEERS=localhost:10001 npm run honestNodesOneMessagePerBlock
Finally you can also explore the current status of the blockchain connecting your favourite web browser to a node (for example, open http://localhost:20004/ following the example above).
The second attempt includes a proof-of-work mechanism so that the network cannot be spammed.
This is work in progress. Stay tunned.