Geth-Developer-Mode

This repository guides the users

1. Create a single-node Ethereum test network with no connections to any external peers.
2. Convert a local Geth into a testnet and deploy a simple smart contract written using the Remix online integrated development environment (IDE).

Note : Starting Geth in developer mode does the following:

• Initializes the data directory with a testing genesis block
• Sets max peers to 0 (meaning Geth does not search for peers)
• Turns off discovery by other nodes (meaning the node is invisible to other nodes)
• Sets the gas price to 0 (no cost to send transactions)
• Uses the Clique proof-of-authority consensus engine which allows blocks to be mined as-needed without excessive CPU and memory consumption
• Uses on-demand block generation, producing blocks when transactions are waiting to be mined

Note : To setup Geth - Refer the steps

Tutorial - 1 : Create a single-node Ethereum test network with no connections to any external peers

Step - 1 : Start Geth in Dev Mode

On the Terminal type :

geth --dev --http --http.api eth,web3,net --http.corsdomain "http://remix.ethereum.org"

• The terminal will display the following logs, confirming Geth has started successfully in developer mode:

Step - 2 : Create an another account using clef

• Open a new terminal, and create a folder for the new node :

mkdir geth_node

clef newaccount --keystore geth_node

Note :

• When prompted type the password.
• For quick reference, note it. Ex. gethnode123
• It generates the Public key and stores the secret key in the folder, geth_node

Step - 3 : Attach a Javascript console and interact with it

geth attach /tmp/geth.ipc

1. To display the existing accounts

eth.accounts

Note:

• This returns an array containing a single address, eventhough no accounts having yet been explicitly created.
• This is the coinbase account.
• The coinbase address is the recipient of the total amount of ether created at the local network genesis.

eth.coinbase==eth.accounts[0]

2. Querying the ether balance of the coinbase account

eth.getBalance(eth.coinbase)/1e18

eth.getBalance(eth.coinbase)

web3.fromWei(eth.getBalance(eth.coinbase))

Note:

• The return value is in units of Wei, which is divided by 118 to give units of ether.
• This can be done explicitly or by calling the web3.FromWei() function

3. Query the ehther balance of the new account created via clef in step 2

eth.getBalance("0x9Ec0a126c014C31456384746d83071F19925aAA2")

4. Send funds from coinbase to the new account created via clef

eth.sendTransaction({from: eth.coinbase, to: "0x9Ec0a126c014C31456384746d83071F19925aAA2", value: web3.toWei(50, "ether")})

• If successful, transaction hash is generated as a repsonse.
• After the funds transfer check the balance of coinbase and the receipient account.

5. To check the transaction details

eth.getTransaction("0x19ec8c7da780b5492c1cca65408f24f1ad8b5a38114a0a5c862e47e875f6b6b8")

• Here, 0x19ec8c7da780b5492c1cca65408f24f1ad8b5a38114a0a5c862e47e875f6b6b8 is the hash generated when the transaction was submitted.

• Now go to the first terminal, where our geth is running in dev mode.
• Here, we can see that the first block is mined.

Tutorial - 2 : Convert a local Geth into a testnet and deploy a simple smart contract written using the Remix

• Create a folder named, geth_node for this tutorial

Step - 1 : Start Geth in Dev Mode

geth --http --http.corsdomain="https://remix.ethereum.org" --http.api web3,eth,debug,personal,net --vmdebug --datadir geth_node --dev console

• The terminal will display the following logs, confirming Geth has started successfully in developer mode.
• The node is waiting for the transaction to mine the block

Step - 2 : Open a Smart Contract in Remix IDE

1. Open the Storage.sol file available at Remix IDE

2. Compile and deploy using Remix IDE

• Click the green play above the contract file

• Click the Deploy menu in Remix IDE.
• In the drop-down menu labelled ENVIRONMENT, select Custom - External Http Provider.

• This will open an information pop-up with instructions for configuring Geth
• Click OK.

• The ACCOUNT field should automatically populate with the address of the account created earlier using the Geth Javascript console.

• This account is same as the one displayed on the Javascript Console

• To deploy Storage.sol, click DEPLOY.
• A transaction occurs and block is mined

• The following logs in the Geth terminal confirm that the contract was successfully deployed.

• To fetch the transaction details from the terminal

3. Interact with contract using Remix

• The contract is now deployed on a local testnet version of the Ethereum blockchain.
• This means there is a contract address that contains executable bytecode that can be invoked by sending transactions with instructions
• After deployment, the Deployed Contracts tab in the sidebar automatically populates with the public functions exposed by Storage.sol.
• To send a value to the contract storage, type a number in the field adjacent to the store button, then click the button. Transaction is submitted and block is mined

Note :

• The from address is the account that sent the transaction,
• the to address is the deployment address of the contract.
• The value entered into Remix is now in storage at that contract address.

• Check the transaction mined and added to the block from the JavaScript Console

• To retrive value, click the button - retrieve

• Alternatively, it can be retrieved using web3.getStorageAt using the Geth Javascript console.

web3.eth.getStorageAt("0xe5c5aaa604c12273b92d8e48d133158abbf44a5f", 0)

• The following command returns the value in the contract storage
• Here, 0xe5c5aaa604c12273b92d8e48d133158abbf44a5f (replace the given address of the receipient in the Geth logs).
• Its the storage address

• Here, 0x000000000000000000000000000000000000000000000000000000000000002d is the hexadecimal value for 45 with which the number was reinitialized.

Note : This tutorial used an ephemeral blockchain that is completely destroyed and started afresh during each dev-mode session.

Acknowledgements

• Go Etehreum - Developer Mode

• Remix Ethereum IDE - Docs

• Basic Writing & Formatting Syntax