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RSK React + Express JS Box

This box comes with everything you need to start using express JS to provide API endpoints to smart contracts and a react app to interact with them on RSK Blockchain. It includes network configurations for Mainnet, Testnet and the SimpleStorage contract as an example to deploy.


  1. NPM (Node Package Manager) and Node.js are needed, though both are usually installed at once.

Go to Node.js if you need to install it.

  1. Truffle

Install Truffle globally:

npm install -g truffle


  1. Create a new folder. For example, create the folder rsk-react-express. Navigate to the folder in the terminal.
mkdir rsk-react-express
cd rsk-react-express
  1. Run the unbox command. It can take some time, as this will install all necessary dependencies.
truffle unbox rsksmart/rsk-react-express-box

A client-server application is generated in the app directory.

This is the result using Windows OS:

truffle unbox

Development console

Truffle has an interactive console that also spawns a development blockchain. This is very useful for compiling, deploying and testing locally.

  1. Run the development console. This command is successful if you see a list of 10 accounts, a mnemonic and the command prompt is now truffle(develop)>
truffle develop

You will now be in the truffle develop REPL with seeded accounts and their associated private keys listed.

C:\RSK\rsk-next>truffle develop

Truffle Develop started at

(0) 0x1056f747cf4bc7710e178b2aeed4eb8c8506c728
(1) 0x45a71c00382c2898b5d6fae69a6f7bfe6edab80c
(2) 0x1596384706dc9ac4cca7f50279a4abe591d6c3fe
(3) 0x9576d0a496b645baa64f22aceb2328e7468d4113
(4) 0xd431572eef7d77584d944c1809398a155e89f830
(5) 0x92c111839718fe0800fadccc67068b40b8524a0f
(6) 0x6da22b5a027146619bfe6704957f7f36ff029c48
(7) 0x2c3a82d8c3993f8c80dcaf91025437bd057df867
(8) 0xc43ae7a44f7deb759177b7093f06512a0a9ff5d7
(9) 0xe61bf00cd7dce248449cfe58f23a4ef7d542bc0b

Private Keys:
(0) f32f32839fe27ad906b63eafb326f26fed95c231e3c5e33c7cdd08f62db63167
(1) ebef990088f27f6ef13b5e52a77d5dcc5a76862a701908c586d01b6fe93562b3
(2) 598ccae5e4436fedeb0e798c0d254789c55a63401ebfc3ae8ddde29634ddfcde
(3) 09934b80f391e0024b8cb00cd73790fdf64c4d0509e144766414fee317cd3f4e
(4) ac745b84b6574b5738d364b43e0d471c9d5107504acc709c90f6f091b78c751b
(5) 449654cde095f2349113ef12a93e139b4302bc95adb3619d08adf53dde9b8847
(6) c217f12a89c352fc70b5f1bd5742314b4fb1bb1e35cb779fdb3c2390106355db
(7) 1d4c74dfa4e99e161130c18cc63938bb120a128cefbf1b9188efc678bf5722cb
(8) 0f44e0becf2e090db498a1b747d2a758fcc81fb0241f350d61117a9c6b1fa82e
(9) 85218c5eec657470dafeb09e6f7101f91d21bfe822fbeeecfc9275f798662a63

Mnemonic: virtual valve razor retreat either turn possible student grief engage attract fiber

⚠️  Important ⚠️  : This mnemonic was created for you by Truffle. It is not secure.
Ensure you do not use it on production blockchains, or else you risk losing funds.

  1. Take a look at the smart contract SimpleStorage.sol. You can check it out in folder contracts.

This smart contract has:

  • A variable storedData to store a number
  • A function get() to return the number stored at variable storedData
  • A function set() to change the number stored at variable storedData

  • Compile and migrate the smart contract. Note, inside the development console we don't preface commands with truffle.

To make sure you're in the development console, the command prompt must be truffle(develop)>


The compile output should be similar to:

truffle compile


And the migrate output should be similar to:

truffle migrate

  1. Running contract tests.

This Truffle box also comes with the file TestSimpleStorage.js for testing the smart contract. You can check it out in the test folder.

Run this command in the development console:


This test output should be similar to:

truffle test

Note the command varies slightly if you're in or outside of the development console.

// inside the development console.

// outside the development console.
truffle test

The application

Our box is a client-server: - Server uses express JS to interact with the smart contract. - Client uses react app.

  1. Running in development mode

In another terminal (i.e. not in the truffle develop prompt), go to the app directory and run the app in development mode.

Do not close the other terminal, which is running the Truffle development console, because it is our Blockchain simulator.

If you close it and then open it again, you need to deploy / migrate the smart contract again too!

cd app
npm run dev

This command executes server and client applications and you can access it in your browser:

Smart contract changes must be manually recompiled and migrated!

NOTE: This box is the starting point for the RSK tutorial using rsk-react-express-box.

  1. Running the production server

You can choose to run only the production server. In another terminal (i.e. not in the truffle develop prompt), go to the app directory and run the app in production mode.

cd app
npm start

If you have yarn installed, you can use yarn start.

Then go to your browser at http://localhost:8080/

localhost port 8080

When you are running only the production server, for any change you need to stop and run the server again for the updates to take effect!

  1. To build the application for production, use the build script in the app folder. A production build will be in the app/dist folder.
npm run build

Take a look in the app/dist folder:

dist folder

Using RSK networks

This Truffle box is already configured to connect to both RSK networks: testnet and mainnet. We need only to update few items:

  • Setup an account & get R-BTC
  • RSK network gas price
  • Your wallet mnemonic
  • Choose the network in the app

Setup an account & get R-BTC

Setup the gas price

Gas is the internal pricing for running a transaction or contract. When you send tokens, interact with a contract, send R-BTC, or do anything else on the blockchain, you must pay for that computation. That payment is calculated as gas. In RSK, this is paid in R-BTC. The minimumGasPrice is written in the block header by miners and establishes the minimum gas price that a transaction should have in order to be included in that block.

To update the minimumGasPrice in our project run this query using cURL:


curl -X POST -H "Content-Type: application/json" \
    --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest",false],"id":1}' \
    > .minimum-gas-price-testnet.json


curl -X POST -H "Content-Type: application/json" \
    --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest",false],"id":1}' \
    > .minimum-gas-price-mainnet.json

This query saved the details of latest block to file .minimum-gas-price-testnet.json or .minimum-gas-price-mainnet.json, respectively.

In the truffle-config.js, we are reading the parameter minimumGasPrice in each json file.

For more information about the Gas and minimumGasPrice please go to the gas page.

Connect to RSK

  1. Copy your mnemonic to truffle-config.js
//Put your mnemonic here, be careful not to deploy your mnemonic into production!
const mnemonic = 'A_MNEMONIC';

Please be aware that we are using HDWalletProvider with RSK Networks derivations path: - RSK Mainnet dpath: m/44’/137’/0’/0 - RSK Testnet dpath: m/44’/37310’/0’/0

For more information check RSKIP57.

  1. Run the development console for any RSK network.
# Console for Testnet
truffle console --network testnet

# Console for Mainnet
truffle console --network mainnet
  1. Migrate the smart contracts. We will do it running the below commands directly in the terminal, without using the truffle console, this is to show you an alternative.

truffle migrate
4. Update express JS component.

The express server uses the web3.js library to interact with the blockchain - writing code that reads and writes data from the blockchain with smart contracts.

Choose which RSK network you would like to connect the server to and update line 11 of the file app/src/server/index.js


const provider = new Web3.providers.HttpProvider("");    


const provider = new Web3.providers.HttpProvider("");

  1. In a terminal, go to the app directory and run the app.

For example, this command will run the production server:

cd app
npm start

Then go to your browser at http://localhost:8080/

Note that when you are connected to an RSK network, you do not need to leave open the Truffle console, because the app is connected via a public node, directly to the network.

Next steps

  • Go to tutorial

Go to the tutorial using rsk-react-express-box to learn more about this project. We covered all the steps with more details, explanations, and images.

  • Find more documentation

Check out the RSK developers portal.

  • Do you have questions?

Ask in the RSK chat.