Version: 0.15.2

Initialising Maker and Taker

This page is part of the typescript tutorial for creating your first COMIT-app, that builds two simple command-line application using the COMIT protocol to execute a Bitcoin to Ethereum atomic swap locally on your machine.

This section of the tutorial shows how to initialise the actors of the trade, the maker and the taker, with the pre-funded accounts of the dev-environment.

In this section we use the Actor interface of the comit-sdk to initialise the maker and taker actors. We will use the Bitcoin and Ethereum accounts created through start-env for initialising the actors.

Through the actor we have access to the wallets and the ComitClient which is used as a wrapper for the communication with cnd.

Initialise the maker actor

info

In this section we focus on the maker side and work on maker.ts

tip

The dependencies to be added are not listed in the code examples. You can check the bottom or this section if you have trouble with imports.

Let's focus on the maker for the beginning. start-env has provided us with two Bitcoin and two Ethereum accounts indexed with 0 and 1. Let's use the Bitcoin and Ethereum account indexed with 0 for the maker.

From the index.js file we already know how to load the environment using the dotenv package. Let's initialise the maker's environment using the same code:

const configPath = path.join(os.homedir(), ".create-comit-app", "env");
dotenv.config({path: configPath});

Because COMIT is a non custodial protocol, the maker needs a Bitcoin and an Ethreum wallet to send transactions into the respective network. In this tutorial we use the Bitcoin and Ethereum wallet provided by the comit-sdk.

First we initialise the Bitcoin wallet using the InMemoryBitcoinWallet provided by the comit-sdk:

const bitcoinWallet = await InMemoryBitcoinWallet.newInstance(
"regtest",
process.env.BITCOIN_P2P_URI!,
process.env[`BITCOIN_HD_KEY_${0}`]!
);
// Waiting for the Bitcoin wallet to read the balance
await new Promise(r => setTimeout(r, 1000));

Then we initialise the EthereumWallet provided bt the comit-sdk:

const ethereumWallet = new EthereumWallet(
process.env.ETHEREUM_NODE_HTTP_URL!,
process.env[`ETHEREUM_KEY_${0}`]!
);

Now we can use the createActor helper function of the comit-sdk to initialise the actor:

let maker = await createActor(
bitcoinWallet,
ethereumWallet,
process.env[`HTTP_URL_CND_${0}`]!
);

Let's print the balance of the maker to see how much BTC and ETH he has before the swap:

console.log(
"[Maker] Bitcoin balance: %f, Ether balance: %f",
(await maker.bitcoinWallet.getBalance()).toFixed(2),
parseFloat(
formatEther(await maker.ethereumWallet.getBalance())
).toFixed(2)
);

Note that we are using the formatEther function from ethers/utils to format the ether properly.

Your maker.ts file should now look like this:

import * as dotenv from "dotenv";
import * as os from "os";
import * as path from "path";
import {createActor, EthereumWallet, InMemoryBitcoinWallet} from "comit-sdk";
import { formatEther } from "ethers/utils";
(async function main() {
console.log("COMIT Maker app");
const configPath = path.join(os.homedir(), ".create-comit-app", "env");
dotenv.config({path: configPath});
const bitcoinWallet = await InMemoryBitcoinWallet.newInstance(
"regtest",
process.env.BITCOIN_P2P_URI!,
process.env[`BITCOIN_HD_KEY_${0}`]!
);
// Waiting for the Bitcoin wallet to read the balance
await new Promise(r => setTimeout(r, 1000));
const ethereumWallet = new EthereumWallet(
process.env.ETHEREUM_NODE_HTTP_URL!,
process.env[`ETHEREUM_KEY_${0}`]!
);
let maker = await createActor(
bitcoinWallet,
ethereumWallet,
process.env[`HTTP_URL_CND_${0}`]!
);
console.log(
"[Maker] Bitcoin balance: %f, Ether balance: %f",
(await maker.bitcoinWallet.getBalance()).toFixed(2),
parseFloat(
formatEther(await maker.ethereumWallet.getBalance())
).toFixed(2)
);
// TODO: Create a simple order service.
// TODO: Create and publish an order so it can be taken by the taker.
// TODO: Execute the order by swapping the assets.
process.exit();
})();

When running yarn run maker you should see the initial bitcoin and ether balance of the maker:

yarn run v1.22.0
$ ts-node ./src/maker.ts
COMIT Maker app
[Maker] Bitcoin balance: 10, Ether balance: 1000
✨ Done in 7.19s.

Initialise the taker actor

info

In this section we focus on the taker side and work on taker.ts

For the taker we have a similar setup as for the maker.

Similar to the maker we have to initialise a Bitcoin and Ethereum wallet with the accounts from the environment. As for the maker we can then create the actor using the comit-sdk's createActor function. Note that we will use the Bitcoin and Ethereum account as well as the cnd instance with index 1 for the taker.

In the end our taker.ts file should look like this:

import * as dotenv from "dotenv";
import * as os from "os";
import * as path from "path";
import {createActor, EthereumWallet, InMemoryBitcoinWallet} from "comit-sdk";
import { formatEther } from "ethers/utils";
(async function main() {
console.log("COMIT Taker app");
const configPath = path.join(os.homedir(), ".create-comit-app", "env");
dotenv.config({path: configPath});
const bitcoinWallet = await InMemoryBitcoinWallet.newInstance(
"regtest",
process.env.BITCOIN_P2P_URI!,
process.env[`BITCOIN_HD_KEY_${1}`]!
);
// Waiting for the Bitcoin wallet to read the balance
await new Promise(r => setTimeout(r, 1000));
const ethereumWallet = new EthereumWallet(
process.env.ETHEREUM_NODE_HTTP_URL!,
process.env[`ETHEREUM_KEY_${1}`]!
);
let taker = await createActor(
bitcoinWallet,
ethereumWallet,
process.env[`HTTP_URL_CND_${1}`]!
);
console.log(
"[Taker] Bitcoin balance: %f, Ether balance: %f",
(await taker.bitcoinWallet.getBalance()).toFixed(2),
parseFloat(
formatEther(await taker.ethereumWallet.getBalance())
).toFixed(2)
);
// TODO: Retrieve an order from the maker.
// TODO: Execute the order by swapping the assets.
process.exit();
})();

When running yarn run taker we should see:

yarn run v1.22.0
$ ts-node ./src/taker.ts
COMIT Taker app
[Taker] Bitcoin balance: 10, Ether balance: 1000
✨ Done in 9.34s.
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