How to run first blockchain hello world program!

I assume that you have read a lot about the block chain technology and where it can be applied. Now you must be wondering where should I develop the Smart Contract and run the program

Do I need to,

• Spent Ether to run program on Ethereum main network to test it
• Download the Ethereum wallet and connect to Ropsten or Rinkeby  test network? Even if you connect to it and download the data from the peers you will find difficulty to execute the program.

Answer is no

Here are the simple steps you need to follow in order to run your first Hello World! etherum smart contract.

Overall Architecture

Step 1 : Setting up testrpc virtual environment

Download the Ethereumjs test rpc Docker image & run it. If you haven’t already installed docker engine follow this instruction.

docker pull silentinfotech/ethereumjs-testrpc
docker run -d -p 8545:8545 silentinfotech/ethereumjs-testrpc:latest -a 10 –debug

When you run the docker it will start the docker container and will forward port 8545 to it.  testrpc is Node.js based ethereum client for development and testing.  Find more information on testrpc from here

Step 2 : Remix IDE

We will use the remix IDE for the ethereum smart contract( In developer language program) development. Navigate to https://remix.ethereum.org/ and allow unsafe script to load.

As a part of first program, We will run hello world “Your first citizen: the greeter” program from ethereum.org. Find more information about hello world program from here

Step 3 : Copy & Paste Hello world contract

Copy “Your first citizen: the greeter” program and paste it on remix IDE window. Contract will be compiled automatically if Auto compile is selected already. Ignore the warning(s) for now.

Step 4 : Run program

Navigate to Run tab from top right corner.  Choose Web3 Provider as environment. Enter appropriate URL – if you are running docker on local computer you won’t need to change the url. We are now connected to testrpc ethereum test environment. We can find the account dropdown auto populated with all test accounts with having 100EHR by default – which are more than sufficient to run the program. ;)

Let’s run the program,

Pass the constructor parameters in create method(e.g “Hello world!”. Click on create, Wow!!! we have generated a first block. You can even call the greet method on newly created block.

You can also read the existing blocks methods/variables by providing block address in At Address text field.

Ethereum Network Charges

In a nutshell, you will be charged when ever you/program will change the state of the variable. e.g Increment value of variable, store the value in variable, destroy value of variable. there is no charge for reading the blocks.

References

https://remix.ethereum.org/

https://www.ethereum.org/greeter