Version: next

Publishing an order

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.

info

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

In this section we create and publish an order that a taker can then fetch from the maker's order HTTP API.

Maker creates an Order

Let's create an Order of 50 ether for 1 bitcoin, meaning that the maker is offering 50 ether and is asking for 1 bitcoin:

// Create an order to be published.
const order = {
id: "123",
validUntil: moment().unix() + 300,
ask: {
nominalAmount: "50",
asset: "ether",
ledger: "ethereum",
},
bid: {
nominalAmount: "1",
asset: "bitcoin",
ledger: "bitcoin",
},
};

Maker publishes the Order

The MakerNegotiator allows us to publish an Order:

// Publish the order so the taker can take it.
makerNegotiator.addOrder(order);

And finally we "tell" the world that we have an order available:

const link = makerNegotiator.getUrl();
console.log(`Waiting for someone to take my order at: ${link}`);

Your COMIt-app could publish this link on a forum or social media so takers can connect to you.

Waiting for a taker

When a taker takes the order created by the maker, it will trigger the swap execution right away. The maker thus has to wait for a taker to take the order to commence with the execution.

In this tutorial the maker is waiting for 10 minutes for a potential taker to taker his order. The maker uses the ComitClient to wait for incoming swaps. Once the taker takes the order he will trigger a swap request in his cnd that will be detected by the maker's cnd.

// Wait for a taker to accept the order and send a swap request through the comit network daemon (cnd).
let swap;
// This loop runs until a swap request was sent from the taker to the maker
// and a swap is waiting to be processed on the maker's side.
while (!swap) {
await new Promise(r => setTimeout(r, 1000));
// Check for incoming swaps in the comit node daemon (cnd) of the maker.
swap = await maker.comitClient.getOngoingSwaps().then(swaps => {
if (swaps) {
return swaps[0];
} else {
return undefined;
}
});
}

Summary

At this stage your maker application should look similar to this:

import * as dotenv from "dotenv";
import * as os from "os";
import * as path from "path";
import {createActor, EthereumWallet, InMemoryBitcoinWallet, MakerNegotiator} from "comit-sdk";
import { formatEther } from "ethers/utils";
import moment = require("moment");
(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)
);
const executionParameters = {
// Connection information for the comit network daemon.
// The maker has to provide this to the taker for the execution phase,
// so that the taker's comit network daemon can message the maker's comit network daemon.
peer: {
peer_id: maker.peerId,
address_hint: maker.addressHint,
},
// The expiry time for the taker.
alpha_expiry: moment().unix() + 7200,
// The expiry time for the maker
beta_expiry: moment().unix() + 3600,
// The network the swap will be executed on.
ledgers: {
bitcoin: { network: "regtest" },
ethereum: { chain_id: 17 },
},
};
const tryParams = { maxTimeoutSecs: 1000, tryIntervalSecs: 0.1 };
const makerNegotiator = new MakerNegotiator(
maker.comitClient,
executionParameters,
tryParams
);
await makerNegotiator.listen(2318, "localhost");
const order = {
id: "123",
validUntil: moment().unix() + 300,
ask: {
nominalAmount: "50",
asset: "ether",
ledger: "ethereum",
},
bid: {
nominalAmount: "1",
asset: "bitcoin",
ledger: "bitcoin",
},
};
makerNegotiator.addOrder(order);
const link = makerNegotiator.getUrl();
console.log(`Waiting for someone to take my order at: ${link}`);
// Wait for a taker to accept the order and send a swap request through the comit network daemon (cnd).
let swap;
// This loop runs until a swap request was sent from the taker to the maker
// and a swap is waiting to be processed on the maker's side.
while (!swap) {
await new Promise(r => setTimeout(r, 1000));
// Check for incoming swaps in the comit node daemon (cnd) of the maker.
swap = await maker.comitClient.getOngoingSwaps().then(swaps => {
if (swaps) {
return swaps[0];
} else {
return undefined;
}
});
}
// TODO: Execute the order by swapping the assets.
process.exit();
})();

When running yarn maker it prints:

yarn run v1.22.0
$ ts-node ./src/maker.ts
COMIT Maker app
[Maker] Bitcoin balance: 10, Ether balance: 1000
Maker's Negotiation Service is listening on localhost:2318.
Waiting for someone to take my order at: http://127.0.0.1:2318

The maker app is now capable for waiting for a taker to initiate the swap for execution. The order is published and a taker can retrieve it, take it and by doing so start the swap execution.

However, the maker does not execute an incoming swap properly yet. Let's add that in the next section before we move on the taker side.

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