Introduction
This page explains how to set up ETN-SC and execute some basic tasks using the command line tools. In order to use ETN-SC, the software must first be installed. There are several ways ETN-SC can be installed depending on the operating system and the user's choice of installation method, for example using a package manager, container or building from source. Instructions for installing ETN-SC can be found on the "Install and Build" pages.
The tutorial on this page assumes ETN-SC client have been installed successfully and that a firewall has been configured to block external traffic to the JSON-RPC port 8545, see Security.
This page provides step-by-step instructions covering the fundamentals of using ETN-SC client. This includes generating accounts, joining the Electroneum network, syncing the blockchain and sending ETN between accounts. This tutorial uses Clef. Clef is an account management tool external to ETN-SC itself that allows users to sign transactions. It is developed by the Geth team and maintained by the Electroneum team.
Prerequisites
In order to get the most value from the tutorials on this page, the following skills are necessary:
Experience using the command line
Basic knowledge about Ethereum, Electroneum Smart Chain and testnets
Basic knowledge about HTTP and JavaScript
Basic knowledge of node architecture
Users that need to revisit these fundamentals can find helpful resources relating to the command line here, Electroneum and its testnets here, http here and Javascript here.
If ETN-SC was installed from source on Linux, make saves the binaries for ETN-SC and the associated tools in /build/bin. To run these programs it is convenient to move them to the top level project directory (e.g. running mv ./build/bin/* ./) from /electroneum-sc. Then ./ must be prepended to the commands in the code snippets in order to execute a particular program, e.g. ./etn-sc instead of simply etn-sc. If the executables are not moved then either navigate to the bin directory to run them (e.g. cd ./build/bin and ./etn-sc) or provide their path (e.g. ./build/bin/etn-sc). These instructions can be ignored for other installations.
Background
ETN-SC is an Electroneum Smart Chain client written in Go. This means running ETN-SC turns a computer into an Electroneum node. Electroneum is a peer-to-peer network where information is shared directly between nodes rather than being managed by a central server. Every 5 seconds one validator node is selected to generate a new block containing a list of transactions that nodes receiving the block should execute. This "block proposer" node sends the new block to its peers. On receiving a new block, each node checks that it is valid and adds it to their database. The sequence of discrete blocks is called a "blockchain".
The information provided in each block is used by ETN-SC to update its "state" - the ETN balance of each account on Electroneum and the data stored by each smart contract. There are two types of account: externally-owned accounts (EOAs) and contract accounts. Contract accounts execute contract code when they receive transactions. EOAs are accounts that users manage locally in order to sign and submit transactions. Each EOA is a public-private key pair, where the public key is used to derive a unique address for the user and the private key is used to protect the account and securely sign messages. Therefore, in order to use Electroneum Smart Chain, it is first necessary to generate an EOA (hereafter, "account"). This tutorial will guide the user through creating an account, funding it with ETN and sending some to another address.
Read more about Electroneum accounts here.
Step 1: Generating accounts
There are several methods for generating accounts in ETN-SC. This tutorial demonstrates how to generate accounts using Clef, as this is considered best practice, largely because it decouples the users' key management from ETN-SC, making it more modular and flexible. It can also be run from secure USB sticks or virtual machines, offering security benefits. For convenience, this tutorial will execute Clef on the same computer that will also run ETN-SC, although more secure options are available (see here).
An account is a pair of keys (public and private). Clef needs to know where to save these keys to so that they can be retrieved later. This information is passed to Clef as an argument. This is achieved using the following command:
The specific function from Clef that generates new accounts is newaccount and it accepts a parameter, --keystore, that tells it where to store the newly generated keys. In this example the keystore location is a new directory that will be created automatically: etn-sc-tutorial/keystore. Clef will return the following result in the terminal:
This is important information. The etn-sc-tutorial/keystore directory will soon contain a secret key that can be used to access any funds held in the new account. If it is compromised, the funds can be stolen. If it is lost, there is no way to retrieve the funds. This tutorial will only use dummy funds with no real world value, but when these steps are repeated on Electroneum mainnet is critical that the keystore is kept secure and backed up.
Typing ok into the terminal and pressing enter causes Clef to prompt for a password. Clef requires a password that is at least 10 characters long, and best practice would be to use a combination of numbers, characters and special characters. Entering a suitable password and pressing enter returns the following result to the terminal:
It is important to save the account address and the password somewhere secure. They will be used again later in this tutorial. Please note that the account address shown in the code snippets above and later in this tutorials are examples - those generated by followers of this tutorial will be different. The account generated above can be used as the main account throughout the remainder of this tutorial. However in order to demonstrate transactions between accounts it is also necessary to have a second account. A second account can be added to the same keystore by precisely repeating the previous steps, providing the same password.
Step 2: Start Clef
The previous commands used Clef's newaccount function to add new key pairs to the keystore. Clef uses the private key(s) saved in the keystore to sign transactions. In order to do this, Clef needs to be started and left running while ETN-SC is running simultaneously, so that the two programs can communicate between one another.
To start Clef, run the Clef executable passing as arguments the keystore file location, config directory location and a chain ID. The config directory was automatically created inside the etn-sc-tutorial directory during the previous step. The chain ID is an integer that defines which EVM compatible network to connect to. Electroneum Smart Chain mainnet has chain ID 52014. In this tutorial Chain ID 5201420 is used which is that of the Electroneum Smart Chain testnet. It is very important that this chain ID parameter is set to 5201420 - Clef uses the chain ID to sign messages so it must be correct. The following command starts Clef on Electroneum Smart Chain testnet:
After running the command above, Clef requests the user to type “ok” to proceed. On typing "ok" and pressing enter, Clef returns the following to the terminal:
This result indicates that Clef is running. This terminal should be left running for the duration of this tutorial. If the tutorial is stopped and restarted later Clef must also be restarted by running the previous command.
Step 3: Start ETN-SC
Etn-sc is the Electroneum Smart Chain client that will connect the computer to the Electroneum network. In this tutorial the network is the Electroneum Smart Chain testnet. Testnets are used to test Electroneum client software and smart contracts in an environment where no real-world value is at risk. To start Etn-sc, run the Etn-sc executable file passing argument that define the data directory (where Etn-sc should save blockchain data), signer (points Etn-sc to Clef), the network ID and the sync mode. For this tutorial, snap sync is recommended. The final argument passed to Etn-sc is the --http flag. This enables the http-rpc server that allows external programs to interact with Etn-sc by sending it http requests. By default the http server is only exposed locally using port 8545: localhost:8545.
The following command should be run in a new terminal, separate to the one running Clef:
Running the above command starts Etn-sc.
By default, Etn-sc uses snap-sync which download blocks sequentially from a relatively recent block, not the genesis block. It saves the data in files in /electroneum-sc/etn-sc-tutorial/etn-sc/chaindata/. Once the sequence of headers has been verified, Etn-sc downloads the block bodies and state data before starting the "state healing" phase to update the state for newly arriving data. This is confirmed by the logs printed to the terminal. There should be a rapidly-growing sequence of logs in the terminal with the following syntax:
This message will be displayed periodically until state healing has finished:
When state healing is finished, the node is in sync and ready to use.
Sending an empty Curl request to the http server provides a quick way to confirm that this too has been started without any issues. In a third terminal, the following command can be run:
If there is no error message reported to the terminal, everything is OK. Etn-sc must be running and synced in order for a user to interact with the Electroneum network. If the terminal running Etn-sc is closed down then Etn-sc must be restarted again in a new terminal. Etn-sc can be started and stopped easily, but it must be running for any interaction with Electroneum to take place. To shut down Etn-sc, simply press CTRL+C in the Etn-sc terminal. To start it again, run the previous command etn-sc --datadir <other commands>.
Step 4: Get Testnet ETN
In order to make some transactions, the user must fund their account with ETN. On the Electroneum mainnet, ETN can only be obtained in three ways:
by receiving it as a reward for validating blocks;
receiving it in a transfer from another Electroneum user or contract;
receiving it from an exchange
On Electroneum testnets, the ETN has no real world value so it can be made freely available via faucets. Faucets allow users to request a transfer of testnet ETN to their account.
The testnet faucet is yet to be rolled out to the public.
Step 5: Interact with Etn-sc
For interacting with the blockchain, Etn-sc provides JSON-RPC APIs. JSON-RPC is a way to execute specific tasks by sending instructions to Etn-sc in the form of JSON objects. RPC stands for "Remote Procedure Call" and it refers to the ability to send these JSON-encoded instructions from locations outside of those managed by Etn-sc. It is possible to interact with Etn-sc by sending these JSON encoded instructions directly over Etn-sc's exposed http port using tools like Curl. However, this is somewhat user-unfriendly and error-prone, especially for more complex instructions. For this reason, there are a set of libraries built on top of JSON-RPC that provide a more user-friendly interface for interacting with Etn-sc. One of the most widely used is Web3.js.
Etn-sc provides a Javascript console that exposes the Web3.js API. This means that with Etn-sc running in one terminal, a Javascript environment can be opened in another allowing the user to interact with Etn-sc using Web3.js. There are three transport protocols that can be used to connect the Javascript environment to Etn-sc:
IPC (Inter-Process Communication): Provides unrestricted access to all APIs, but only works when the console is run on the same host as the etn-sc node.
HTTP: By default provides access to the eth, web3 and net method namespaces.
Websocket: By default provides access to the eth, web3 and net method namespaces.
This tutorial will use the HTTP option. Note that the terminals running Etn-sc and Clef should both still be active. In a new (third) terminal, the following command can be run to start the console and connect it to Etn-sc using the exposed http port:
This command causes the terminal to hang because it is waiting for approval from Clef. Approving the request in the terminal running Clef will lead to the following welcome message being displayed in the Javascript console:
The console is now active and connected to Etn-sc. It can now be used to interact with the Electroneum (testnet) network.
List of accounts
In this tutorial, the accounts are managed using Clef. This means that requesting information about the accounts requires explicit approval in Clef, which should still be running in its own terminal. Earlier in this tutorial, two accounts were created using Clef. The following command will display the addresses of those two accounts and any others that might have been added to the keystore before or since.
The console will hang, because Clef is waiting for approval. The following message will be displayed in the Clef terminal:
Entering "y" approves the request from the console. In the terminal running the Javascript console, the account addresses are now displayed:
It is also possible for this request to time out if the Clef approval took too long - in this case simply repeat the request and approval. Accounts can also be listed directly from Clef by opening a new terminal and running clef list-accounts --keystore <path-to-keystore>.
Checking account balance.
Having confirmed that the two addresses created earlier are indeed in the keystore and accessible through the Javascript console, it is possible to retrieve information about how much ETN they own. The testnet faucet should have sent 5 ETN to the address provided, meaning that the balance of one of the accounts should be at least 5 ETN and the other should be 0. There are other faucets available that may dispense more ETN per request, and multiple requests can be made to accumulate more ETN. The following command displays the account balance in the console:
There are actually two instructions sent in the above command. The inner one is the getBalance function from the eth namespace. This takes the account address as its only argument. By default, this returns the account balance in units of Wei. There are 1e-18 Wei to one ETN. To present the result in units of ETN, getBalance is wrapped in the fromWei function from the web3 namespace. Running this command should provide the following result, assuming the account balance is 1 ETN:
Repeating the command for the other (empty) account should yield:
Send ETN to another account
The command eth.sendTransaction can be used to send some ETN from one address to another. This command takes three arguments: from, to and value. These define the sender and recipient addresses (as strings) and the amount of Wei to transfer. It is far less error prone to enter the transaction value in units of ETN rather than Wei, so the value field can take the return value from the toWei function. The following command, run in the Javascript console, sends 0.1 ETN from one of the accounts in the Clef keystore to the other.
Note that the addresses here are examples - the user must replace the address in the from field with the address currently owning 1 ETN, and the address in the to field with the address currently holding 0 ETN.
Note that submitting this transaction requires approval in Clef. In the Clef terminal, Clef will prompt for approval and request the account password. If the password is correctly entered, Etn-sc proceeds with the transaction. The transaction request summary is presented by Clef in the Clef terminal. This is an opportunity for the sender to review the details and ensure they are correct.
After approving the transaction, the following confirmation screen in displayed in the Clef terminal:
In the Javascript console, the transaction hash is displayed. This will be used in the next section to retrieve the transaction details.
It is also advised to check the account balances using Etn-sc by repeating the instructions from earlier. At this point in the tutorial, the balances of the two accounts in the Clef keystore should have changed by ~0.1 ETN (the sender's balance will have decremented by a little over 0.1 ETN because some small was amount paid in transaction gas).
Checking the transaction hash
The transaction hash is a unique identifier for this specific transaction that can be used later to retrieve the transaction details. The same information can also be retrieved directly from the Etn-sc node. The hash returned in the previous step can be provided as an argument to eth.getTransaction to return the transaction information:
This returns the following response (although the actual values for each field will vary because they are specific to each transaction):
Using Curl
Up to this point this tutorial has interacted with Etn-sc using the convenience library Web3.js. This library enables the user to send instructions to Etn-sc using a more user-friendly interface compared to sending raw JSON objects. However, it is also possible for the user to send these JSON objects directly to Etn-sc's exposed HTTP port. Curl is a command line tool that sends HTTP requests. This part of the tutorial demonstrates how to check account balances and send a transaction using Curl.
Checking account balance
The command below returns the balance of the given account. This is a HTTP POST request to the local port 8545. The -H flag is for header information. It is used here to define the format of the incoming payload, which is JSON. The --data flag defines the content of the payload, which is a JSON object. That JSON object contains four fields: jsonrpc defines the spec version for the JSON-RPC API, method is the specific function being invoked, params are the function arguments, and id is used for ordering transactions. The two arguments passed to eth_getBalance are the account address whose balance to check and the block to query (here latest is used to check the balance in the most recently mined block).
A successful call will return a response like the one below:
The balance is in the result field in the returned JSON object. However, it is denominated in Wei and presented as a hexadecimal string. There are many options for converting this value to a decimal in units of ETN, for example by opening a Python console and running:
This returns the balance in ETN:
Checking the account list
The curl command below returns the list of all accounts.
This requires approval in Clef. Once approved, the following information is returned to the terminal:
Sending Transactions
Sending a transaction between accounts can also be achieved using Curl. Notice that the value of the transaction is a hexadecimal string in units of Wei. To transfer 0.1 ETN, it is first necessary to convert this to Wei by multiplying by 10^18 then converting to hex. 0.1 ETN is "0x16345785d8a0000" in hex. As before, update the to and from fields with the addresses in the Clef keystore.
This requires approval in Clef. Once the password for the sender account has been provided, Clef will return a summary of the transaction details and the terminal that made the Curl request will display a response containing the transaction hash.
Summary
This tutorial has demonstrated how to generate accounts using Clef, fund them with testnet ETN and use those accounts to interact with the Electroneum Smart Chain (testnet) through the Etn-sc node. Checking account balances, sending transactions and retrieving transaction details were explained using the web3.js library via the Etn-sc console and using the JSON-RPC directly using Curl. For more detailed information about Clef, please see the Clef docs.
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