Exploring the Blockchain – Part1

A few days ago I decided that I wanted to learn more about the Blockchain. So I started reading various documentations, browsed through GitHub, watched video’s online and finally took the online training at the Microsoft Virtual Academy “Microsoft Blockchain as a Service”. I guess this is only the beginning as there is so much more to explore in this field. But today I want to share with you the first steps I took trying to understand how this all works.

The first thing I needed was a Blockchain where I can play around. When you download the Ethereum Wallet you can access the Main network, the test network or run a local blockchain node, but while I was looking into that, I came across a much easier and (for me as a Blockchain newbie) more comprehensive solution called “Ganache” Ganache is a one click ethereum blockchain which you can use to run tests, execute commands, and inspect state while controlling how the chain operates.

Ganache is available for Windows, Mac and Linux. I am going to use the Windows version. here. So let’s install it.

When starting the Ganache Application , it automatically creates 10 accounts. Each account gets an initial 100 ETH assigned.

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There is no need to run a miner for generating new blocks, since it has an build in miner.

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When we select the Blocks option, we see that the first block has been created.

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Since we haven’t executed any transactions on the blockchain yet, the block has no transactions.

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Okay, so we now have a local blockchain running that is waiting for some transactions. We could now setup some wallets for the test accounts and transfer ETHs, but since I am on a journey to learn how things actually work, I came across the web3 JavaScript API for Ethereum.

If you haven’t installed Node.js yet, you can download it from here: https://nodejs.org/en/download/

Next open a command prompt and create a folder like C:\DEV\Web3NodeJS

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Then install the Ethereum JavaScript API with the following command:

npm install web3@0.20.3

(I specified the version, as this is the version where things worked for me).

Once installed, you should have the following content within the folder.

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Now let’s start Node. Enter ‘Node’ at the command prompt.

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then enter the following 2 lines of code:

Web3 = require(‘web3’);

web3 = new Web3(new Web3.providers.HttpProvider(http://localhost:7545));

Note that the above specified port relates to the local RPC server.

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Now that we have a connection, we can start communicating with our local Blockchain. Let’s start with some simple commands:

at the prompt enter: web3.eth

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to get a list of all the accounts enter.

web3.eth.accounts

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These should be the same accounts that you see in the Ganache application. Now let’s take a look at the balances of the first 3 accounts.

web3.eth.getBalance(‘0x627306090abab3a6e1400e9345bc60c78a8bef57’)
web3.eth.getBalance(‘0xf17f52151ebef6c7334fad080c5704d77216b732’)
web3.eth.getBalance(‘0xc5fdf4076b8f3a5357c5e395ab970b5b54098fef’)

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And now we transfer some ETH from one account to another. We send 5 ETH from the 3rd account to the 2nd account.

web3.eth.sendTransaction({from: ‘0xC5fdf4076b8F3A5357c5E395ab970B5B54098Fef’, to: ‘0xf17f52151ebef6c7334fad080c5704d77216b732’, value: web3.toWei(5, ‘ether’), gasLimit: 21000, gasPrice: 20000000000})

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Switch back to the Ganache application and check the account balance.

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The next block has been created which includes the transaction.

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Now let’s take a look at the transaction itself.

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1. the transaction ID

2. The sender address

3. The receiver address

4. the value we transferred = 5

Now let’s switch back to the Node console and enter the following command to retrieve the details for Block 1.

web3.eth.getBlock(1)

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Now let’s look at the transaction details. Note that I took the transaction ID from the output above.

web3.eth.getTransaction(‘0x48296c2076ed3ecdafef03e85ae012025431eee89688de251506546232edf0ce’)

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That’s it for today, I hope you enjoyed the article. I am currently looking at creating contracts within Ethereum, I’ll share my learnings with that anytime soon.

Resources

What is Ethereum?
http://ethdocs.org/en/latest/introduction/what-is-ethereum.html

Web3.js
https://github.com/ethereum/web3.js

Ganache
http://truffleframework.com/ganache/

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