smfaizalkhan / ethreum

Ethreum

Setting up a private BlockChain Network using Ethereum

1)Install Go CLient for Ethereum (Geth )

-sudo apt-get install software-properties-common -sudo add-apt-repository -y ppa:ethereum/ethereum -sudo apt-get update -sudo apt-get install ethereum

Confirm it by typing geth --help

2. Setting up the ehtereum home sudo mkdir ethereum sudo gedit ~/. profile export ethereum_home="/home/faizal/ethereum"

3)Setting up a Network

   To get a Hands-on  ,i have set-up a virtual machine hosting ubuntu where ehtereum and geth is installed following the above command.

Creating a Genesis file (Any Blockchain N/W needs to have a genesis block for the chain to link the subsequent blocks)
  The genesis file shoud be the same in both the machines
        genesis.json
		  {
	    "config": {
		"chainId": 1092,
		"homesteadBlock": 0,
		"eip155Block": 0,
		"eip158Block": 0
	    },
	    "nonce": "0x0000000000000042",     
	    "alloc": {
	       
	    },
	    "timestamp": "0x00", 
	    "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000", 
	    "extraData": "0x3535353535353535353535353535353535353535353535353535353535353535", 
	    "gasLimit": "0x8000000", 
	    "difficulty": "0x400", 
	    "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000", 
	    "coinbase": "0x3333333333333333333333333333333333333333"  
	}  

   
             chainId is the ID for the Chain N/W,
	 nonce is for POW purpose nonce and mixhash are used to prove some computataion has be done to solve  				 mathematical  problem as mentioned in yellow Paper,
	 ParentHash is 256 bit hash and in case of  genesis file it is set to 0,
	 difficulty is set to minimal 

4. Instructions for dataDir

   The following instructions has to be done  in both machines.
   

   a) Copy the gensis.json file into ethereum_home in both the machines. b) Initialise the block -- sudo geth --datadir "$ethereum_home/node1" init "$ethereum_home/genesis.json c) Start the N/W mentioning port and specify networkid sudo geth --datadir "$ethereum_home/node1" --port 30304 --nodiscover --rpc --rpcport 8545 --rpccorsdomain "*" -networkid 1092 console d)In the 2nd machine console type admin.nodeInfo.enode and copy the enode and replace [:] with ip address of the machine

    "enode://6b17a2de281cb1aebbc3dd065472c0f9e293c31074b9ba3850003a5b08a55a0e0563ff08c4e7da9580caac2e8881611ed9cdbb4fd593e7638878d5e4586cf8fd@192.168.0.118:30304?discport=0"
   

   e) Add second machine as peer in first node

        admin.addPeer("enode://6b17a2de281cb1aebbc3dd065472c0f9e293c31074b9ba3850003a5b08a55a0e0563ff08c4e7da9580caac2e8881611ed9cdbb4fd593e7638878d5e4586cf8fd@192.168.0.118:30304?discport=0")
   

   d)Verifying the Peers

    admin.peers function will display the list of peers
    net.listening will let out a boolean indicating its listening value
    net.peerCount will display the peer count value
   

   e) Create a Acccount Personal.newAccount(),enter a passPhrase Remeber the passphrase

   f) miner.start to start the computation process

5. Smart Contract

   Smart contracts is usually written in Solidity language,It can be written in online JIT Solidity compiler or using truffle I will proceed with truffle

6)Installing Truffle

We need nodejs to install truffle as it is a npm project

   npm install -g truffle  (Truffle installed on a golobal level)

7)Writing smart contract

 a) create a directory for smart contract and from the terminal type truffle init which will create the Dapp folder structure
 b) Editor of your choice.I ahve used Sublime Text 3
       In sublime text 3 ,to get syntax highligting and code completion

      --  In sublime text 3 enter Ctrl+shift+P to install the package,select ethereum 

 c) Sample contract 

    Balance.sol
      
		    pragma solidity ^0.4.4;

	contract Balance{

	 uint public amount;

	 function Balance(uint _amount){
	 	amount = _amount;
	 }	

	 function withDrawAmount(uint _amount){
	 	amount = -_amount;
	 }

	 function addAmount(uint _amount){
	 	amount = +_amount;
	 }
	}

d)  Navigate to  migration folder ,open the file deploy_contracts.js file and add the line 

       deployer.deploy(Balance);        comment other lines

c) compile it using the command "truffle compile"

d) Depoy file to deploy the smart contract is truffle.js ,sample file as below

		module.exports = {
	  networks: {
	    development: {
	      host: "localhost",
	      port: 8545,
	      network_id: "*" // Match any network id
	    }
	  }
	};

e) Command to deploy is "truffle migrate"