Setup and run an Ethereum Private Network

Content

• eth_common/ - genesis.json file, setup new coinbase (base account), password file.
• Dockerfile-gethlatest - Image of ethereum node container using the latest stable version of geth.
• Dockerfile-geth1.7.3 - Image of ethereum node container using the version 1.7.3 of geth (Can easily be modified to support another specific version of geth).
• node_client/ - JSON-RPC client writen in NodeJS.

Start a private network

1. The docker-compose file starts 2 nodes (default) on the privtnet docker network.

$ docker network create privtnet
$ docker-compose up -d

2. The two nodes are launched in a dedicated docker network, BUT they need to see each other as peer nodes in the ethereum network. Thus, we need to add them as peers (manually):

• To get a mapping container=IPAddress, run:

  docker network inspect privtnet --format='{{range .Containers}}{{.Name}}={{.IPv4Address}}  ||  {{end}}'

• Attach to each container, by running docker attach [containerID]
• Start the node and get access to the geth console by running ./startNode.sh
• On each node, run admin.nodeInfo.enode in the geth console.
• In the geth console of node1, declare a variable enode, which value is equal to the result of admin.nodeInfo.enode of the node2, and REPLACE the [::] part by the IP of the docker container running node2 (see in docker network inspect privtnet). Do the same thing with node2.
• Add the node as peer to the other node, by running admin.addPeer(enode) in each console.
• List the peers on each node, by running: admin.peers in the geth console.
• At that point, both nodes should see each other as peers.

3. Run the commands: eth.hashrate and eth.blockNumber (If both outputs are 0, then wait for a few seconds/minutes). Both outputs should be quite close from each other.

Play with the nodes

1. Check the balance of the different accounts from your geth console:

function checkBalances() {
    var totalBalance = 0;
    for (var accountNb in eth.accounts) {
        var account = eth.accounts[accountNb];
        var accountBalance = web3.fromWei(eth.getBalance(account), "ether");
        totalBalance += parseFloat(accountBalance);
        console.log("eth.accounts[" + accountNb + "]: \t" + account + " \t balance: " + accountBalance + " ether");
    }
    console.log("Total balance: " + totalBalance + " ether");
};

Inlined function to copy and paste directly in your console:

function checkBalances(){var e=0;for(var a in eth.accounts){var t=eth.accounts[a],c=web3.fromWei(eth.getBalance(t),"ether");e+=parseFloat(c),console.log("eth.accounts["+a+"]: \t"+t+" \t balance: "+c+" ether")}console.log("Total balance: "+e+" ether")}

2. Launch the node client to get the latest blocks. (Note: This has to be launched from another terminal on the host machine for instance):

cd node_client && node index.js

3. Inspect some blocks from one of the node:

eth.getBlock([blockNumber])

4. Do some transactions between one account to another:

• Create a second account on your node: personal.newAccount('[youPassword]')
• Verify that your account has been created properly. The command eth.accounts should output 2 accounts.
• Send some ether from eth.account[0] to eth.account[1]. To do so, you need to:

• Unlock the account you want to send the ethers from: Run personal.unlockAccount(eth.accounts[0]), and enter your passphrase.
• Perform the transaction: set the amount var amount = web3.toWei(0.01, "ether"), and run eth.sendTransaction({from:eth.accounts[0], to:eth.accounts[1], value: amount})

5. Once your transaction is made, you can inspect it, by running eth.getTransaction("[hashOfTheTX]"), where hashOfTheTX is the hash that has been printed on the Geth console when you submitted your transaction at step 4.
6. Next steps: Play around and make you familiar with geth (Inspect the blocks, inspect the TX and so on...)

Use Curl to interact with your nodes

The template is:

$ curl -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"[method to call]","params":[listOfParameters], "id": 1}' http://[yourNodeURL]:[yourNodePort]

Here is an example requesting the rpc modules via curl.

$ curl -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"rpc/_modules","params":[], "id": 1}' http://localhost:8549

See: http://www.jsonrpc.org/specification and https://github.com/ethereum/wiki/wiki/JSON-RPC for more details.

Sources

• https://gist.github.com/fishbullet/04fcc4f7af90ee9fa6f9de0b0aa325ab
• https://github.com/ethereum/go-ethereum/wiki/Managing-your-accounts
• https://media.consensys.net/how-to-build-a-private-ethereum-blockchain-fbf3904f337