BlockChain_MiniDemo

Reference

BlockChain Set-up

npm install
npm install crypto-js --save
npm install mocha --save   //(point to node_modules dir)

Testing (Blockchain)

-- point to root dir

./node_modules/mocha/bin/mocha test

Network Set-up

(point to node_modules dir)

npm install express --save  // enable api with express
npm install body-parse --save // parse request arguments
npm install multer --save // parse request arguments

Each node in the network has its own express endpoints and we use the url-parse package to parse the peer and add its host to the peers set:

npm install url-parse --save

Testing (Network)

In order to test the blockchain network we need to be able to connect to the API over HTTP. curl is used in this tutorial, Postman also works.

start the server

node src/server.js

Should start successfully a server listening on port 5000.

mine a new block call the /mine endpoint.In a new terminal tab, run the following curl command:

curl -X POST "localhost:5000/mine" -H 'Content-Type: application/json' -d'
{
    "data": "Mine block no 1"
}
'

use /blocks endpoint to confirm blocks mined

curl -X GET "localhost:5000/blocks" -H 'Content-Type: application/json'

So far we have a node running on a machine with 2 blocks (or more, depending on how many times the curl POST command was ran)

start up another server on a different port

node src/server.js port=5001

add the first node to the new server as a peer using the /peers/add endpoint

curl -X POST "localhost:5001/peers/add"  -H 'Content-Type: application/json' -d'
{
    "peers":  ["http://localhost:5000"]
}
'

mine a new block on the second node

curl -X POST "localhost:5001/mine" -H 'Content-Type: application/json' -d'
{
    "data": "Mine block on second server"
}
'

now we have nodes in the network, where the second one is a fork from the genesis block. Time to move onward to the consensus mechanism.

Consensus

longest valid chain rule in the network the valid chain with the most work is recognised as the main chain. All new blocks would thus be added to this by any other node in the network Add:

A new endpoint to our API /peers/check
A new function to our blockchain class checkLongestChain which is called via the API and return true if our set of blocks is the longest chain
A new function in our consensus implementation checkLongestChain which called the /blocks endpoint for each peer and checks the length of their chain

Install the node-fetch package

npm install node-fetch --save

More Testing

Start node 1 server:

node src/server.js

Mine a few blocks (say 2):

curl -X POST "localhost:5000/mine" -H 'Content-Type: application/json' -d'
{
    "data": "Mine a block on node 1"
}
'

Start node 2 server:

node src/server.js port=5001

Add nodes as peers of each other

curl -X POST "localhost:5000/peers/add"  -H 'Content-Type: application/json' -d'
{
    "peers":  ["http://localhost:5001"]
}
'
curl -X POST "localhost:5001/peers/add"  -H 'Content-Type: application/json' -d'
{
    "peers":  ["http://localhost:5000"]
}
'

Call /peers/check on node 2: (this will result in the chain on node 2 being replaced with the chain on node 1)

curl -X GET "localhost:5001/peers/check"

Mine a new block on node 2 would now mean adding block number 4

curl -X POST "localhost:5001/mine" -H 'Content-Type: application/json' -d'
{
    "data": "Mine a block on node 2"
}
'

TakaiKinoko/BlockChain_MiniDemo