This is a simple Node JS development of a blockchain.

It contains:

• a back-end implementation of adding nodes to a blockchain, mining blocks and broadcasting transactions
• an HTML/AngularJS page with a Block Explorer

Be sure to install Node in your machine. Then, clone or fork this repository and run npm i to install all the dependencies.

Open five terminals, and in each one of then launch a different terminal:

• run npm run node_1 to launch node number 1 at localhost:3001
• run npm run node_2 to launch node number 2 at localhost:3002
• run npm run node_3 to launch node number 3 at localhost:3003
• run npm run node_4 to launch node number 4 at localhost:3004
• run npm run node_5 to launch node number 5 at localhost:3005

Open Postman and do a POST to localhost:3001/register-and-broadcast-node with the following request body

{ "newNodeUrl": "http://localhost:PORT" }

where PORT is the port of the node (3002 to 3005)

After this three steps, you will be able to create and broadcast transactions, as well as mine blocks.

GET /blockchain

Example: open an API client and do a GET request to http://localhost:3001/blockchain

POST /transaction/broadcast

Example: open an API client and do a POST request to http://localhost:3002/transaction/broadcast with a request body such as:

{ "amount": 120, "sender": "DRFTSGDGDFGDFG", "recipient": "AZODAZIODJOIAZDJ" }

This should add the transaction to the pending transactions collection and broadcast this information to all nodes in the network.

GET /mine

Example: open an API client and do a GET request to http://localhost:3001/mine

Then check the blockchain in all of the nodes.

GET /consensus

If there are nodes with different chains, we can reach a consensus calling this endpoint in one of them. For example: http://localhost:3005/consensus

GET /transaction/:transactionId

For example: http://localhost:3001/transaction/trans123 will retrieve the detailed information of transaction trans123

GET /block/:blockHash

For example: http://localhost:3001/block/0000e27f4d52a5d17d8d3eeaf93ab037e173d09412f018bf0da085bfd72d66c3 will retrieve the detailed information of block with hash 0000e27f4d52a5d17d8d3eeaf93ab037e173d09412f018bf0da085bfd72d66c3

GET /address/:address

For example: http://localhost:3001/address/ba345540e29011e8adb803f70749c524 will retrieve the list of all transactions and the balance of member ba345540e29011e8adb803f70749c524

Last but not least, with the block explorer you can have a web page to check informations regarding transactions, address or blocks.

Once you start the nodes, you can browse, for example http://localhost:3001/block-explorer to access it.

Select in the kind of information you want to find in the list, and write down in the input field the identifier of the object whose information you are looking for, and click on the "Search" button.

For example, if you select "Address" and in the input field you write ba345540e29011e8adb803f70749c524 on the upper input field, when you click the "Search" button you will find all the transactions and balance of the address ba345540e29011e8adb803f70749c524 in the results area.