Setup your Ethereum node with geth on the Ropsten test network

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This is a step by step guide to setup your own Ethereum node on the Ropsten network. At the end of this guide you’ll be able to:

  • Run your own ethereum node synced with the Ropsten testnet network
  • Making sure to keep the node in sync with the blockchain on the network
  • Be able to communicate via the JSON-RPC API of your own node
  • Using the same method to run your node on the main network

Why do you want run your own node?

  • Once your dAPP and Smart Contract are working locally, you’ll want to test it on a real network with (almost) real condition.
  • There is a service called Infura, allowing you to communicate easily with Ropsten via json-rpc without having to setup your own node. However, Infura doesn’t allow you to listen to events that your smart contract could trigger. Events are useful when you want start to do some fancy thing like real time data replication on a second database or simply notify your users in your dApp. If you do not need events, you should definitely use Infura :)
  • An other reason would be to mine some new block and earn some money. But I won’t cover that topic here

Prerequisite :

  • Your own server. I have a Digital Ocean one. A good droplet to use is the one with 2GB memory and 50GB of diskspace. I also pick Ubuntu 16.04 for the OS. If you’re a student, you can have a nice $50 free credits for testing purpose.
  • At least 10GB availlable of space disk. The Ropsten chain takes about 9.0GB on my server disk (4rd February 2018) . The “real” ethereum blockchain requires about 50GB of diskspace.

Step1: Setup geth (go ethereum)

geth will allow you to sync the Ethereum blockchain, but also and run a rpc client

To set that up :

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

I’m using geth version: 1.7.3-stable for this guide

Some people might prefer parity. This guide will focus on geth

Step2: Sync your node with the Ropsten network

The sync will take about 4 hours. I’m running the command in a screen console, just in case I lose the ssh connection or want to do something else in the server. You can also use tmux if you prefer.

Optional : Before syncing it , make sure to remove any previous data you might have locally. (don’t run that if you’re in a middle of a sync, or you’ll need to start again) :

geth --testnet removedb

Then sync the full ropsten blockchain network:

geth --testnet --fast --bootnodes "enode://20c9ad97c081d63397d7b685a412227a40e23c8bdc6688c6f37e97cfbc22d2b4d[email protected]52.169.14.227:30303,enode://6ce05930c72abc632c58e2e4324f7c7ea478cec0ed4fa2528982cf34483094e9c[email protected]13.84.180.240:30303" console

Those flags are really important for the first run. They are useful for:

  • --testnet : you’ll sync with the Ropsten network. Alternatively you can use other flags
  • --fast : you’re enabling fast syncing
  • --bootnodes : Through these bootnodes a node can join the network and find other nodes. The one I’ve given are valid for the 3rd Feb 2018, and might change in the future. Check the ropsten official repo to get the updated bootnodes.
  • console: I attached the console to know the current state of the sync . Without that, you’ll be a bit blind on the progress of the sync

The Ethereum blockchain will store the data in the default directory (/YOUR_HOME/.ethereum/testnet/geth/chaindata). You can also check the size of the blockchain with du -hs /YOUR_HOME/.ethereum/testnet/geth/chaindata

Note: geth will run indefinitely until you exit with ctrl-c. It needs to keep your node in sync with the network with all new data. So once you run the command, geth kept the --fast and --bootnodes xxxx in memory. So you can safely run geth (with always keeping the network you want to use , --testnet in that case)

(optional) Step2.1: restart the sync when geth error-out

It happened to me (several times) that geth errored-out during the sync. I didn’t find out why, but simply run the following command, and the sync will continue from where it exited :

geth --testnet console

Note: I didn’t specify the --bootnodes and --fast flags

If like me, geth kept erroring out, and you do not have time to monitor the sync, here a command you can run to run that command indefinitely if it errors-out:

until geth --testnet  console; do
  echo geth sync failed, retrying in 10 seconds...
  sleep 10
done

You can then come back few hours later without worrying if the sync went well :) Also, having geth that keep exiting might be a sign that oyu do not have enough memory. I recommend at least 2GB.

(optional) Step2.2: Check the progress of the sync

Because you attached the console to the geth command with the console flag, you’ll be able to know the progress of the sync by typing that following command inside the geth console : > eth.syncing It will return :

{
  currentBlock: 914011,
  highestBlock: 2579729,
  knownStates: 7383,
  pulledStates: 480,
  startingBlock: 914001
}

Note: highestBlock: 2579729 should match (even be greater) than the last block in Ropsten Etherscan website

Step3: Activate the JSON-RPC API (and keep your node in sync)

As a developer, sooner or later you’ll want to start interacting with Geth and the Ethereum network via your own programs and not manually through the console. geth has built in support for a JSON-RPC based APIs (standard APIs and Geth specific APIs). These can be exposed via HTTP, WebSockets and IPC (unix sockets on unix based platforms).

geth --testnet --rpc --rpcapi "eth,net,web3" --rpccorsdomain '*' --rpcaddr 0.0.0.0 --rpcport 8080
  • --rpc Enable the HTTP-RPC server
  • --rpcaddr HTTP-RPC server listening interface
  • --rpcport HTTP-RPC server listening port
  • --rpcapi API’s offered over the HTTP-RPC interface
  • --rpccorsdomain * for allowing everything access to it

When running that command, geth will keep your node in sync with the network. You can let that one run in a screen or tmux terminal to keep it alive. The best thing would be to let the process managed by supervisord or systemd

Step4: Query the JSON-RPC API

You can test if the api is working with curl:

curl -X POST --data '{"jsonrpc":"2.0","method":"net_version","params":[],"id":67}' http://0.0.0.0:8080

If all is fine, you should get a response that looks like :

{"jsonrpc":"2.0","id":67,"result":"3"}

(optional) Open the firewall

If you want your dApp or Metamask to communicate with your node, you’ll need to open the port of your server. On Digital Ocean, it’s quite easy via their console. With my example, I’ve opened the port 8080 in the Inbound settings.

Then you can query the api via :

curl -X POST --data '{"jsonrpc":"2.0","method":"net_version","params":[],"id":67}' http://X.X.X.X:8080

with replacing X.X.X.X the ip of your instance.

Also, please understand the security implications of opening up an HTTP/WS based transport before doing so! Hackers on the internet are actively trying to subvert Ethereum nodes with exposed APIs!

Run on the main Ethereum network

As many may have guess, you’ll just need to remove the --testet flag to all commands I’ve shown you to be able to sync to the main Ethereum network! That’s all!

Also, you can change the --testnet flag to --rinkeby to use the Rinkeby network. The main differences with Ropsten are detailed here.

Curious about what I’m building?

I’m building a side project based on the ethereum network. Wondering what is it? Follow me on Twitter :)

Next blog post?

I hope this guide was helpful for anyone starting. Please let me know if there is any mistakes. I’m also thinking writing about:

  • How to run easily your own ETH blockchain with truffle and ganache on a remote server. That one is useful if you do not want to sync the full chain, and have the same blockchain available quickly for your teamate.
  • How to have a realtime data replication of your smart contract using events to an other DB. That one could be useful because querying the Ethereum blockchain might not be as fast and easy as we wish :)
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