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SDK

The Connext SDK allows developers to interact with the Connext protocol in standard Node.js or web environments.

Cross-Chain Transfer​

This example demonstrates how to execute an xcall to transfer funds from a wallet on the source domain to the same address on the destination domain.

1. Setup​

Install Node.js and use Node.js v18. Follow the instructions to install nvm, a node version manager, which will make switching versions easier.

Create a project folder and initialize the package. Fill out the project information as you please.

mkdir connext-sdk-example && cd connext-sdk-example
npm init

We'll be using TypeScript so install the following and generate the tsconfig.json file.

npm install --save-dev @types/node @types/chai @types/mocha typescript 
npx tsc --init # or `yarn tsc --init`

We want to use top-level await so we'll set the compiler options accordingly.

tsconfig.json
{
  "compilerOptions": {
    "outDir": "./dist",
    "target": "es2017",
    "module": "esnext",
    "moduleResolution": "node",
    "allowSyntheticDefaultImports": true
  },
  "exclude": ["node_modules"]
}

Add type and scripts as root-level entries to package.json - they may already exist, so just replace them with the following.

package.json
{
  ...
  "type": "module",
  "scripts": {
    "xtransfer": "tsc && node dist/xtransfer.js"
  }
  ...
}

2. Install dependencies​

Install the latest beta version of Connext SDK and ethers.

npm install @connext/sdk
npm install [email protected]^5

3. The code​

First, we'll configure the SDK. Create a config.ts file with the following contents.

config.ts
import { SdkConfig } from "@connext/sdk";import { ethers } from "ethers";// Create a Signer and connect it to a Provider on the sending chainconst privateKey = "<PRIVATE_KEY>";let signer = new ethers.Wallet(privateKey);// Use the RPC url for the origin chainconst provider = new ethers.providers.JsonRpcProvider("https://rpc.ankr.com/eth_goerli");signer = signer.connect(provider);const signerAddress = await signer.getAddress();const sdkConfig: SdkConfig = {  signerAddress: signerAddress,  // Use `mainnet` when you're ready...  network: "testnet",  // Add more chains here! Use mainnet domains if `network: mainnet`.  // This information can be found at https://docs.connext.network/resources/supported-chains  chains: {    1735353714: { // Goerli domain ID      providers: ["https://rpc.ankr.com/eth_goerli"],    },    1735356532: { // Optimism-Goerli domain ID      providers: ["https://goerli.optimism.io"],    },  },};export { signer, sdkConfig };

Replace <PRIVATE_KEY> with your own private key on line 5.

Notice that the config supports Goerli and Optimism-Goerli. We've also hard-coded the origin chain provider on line 84.

Now create a xtransfer.ts file with the following:

xtransfer.ts
import { create } from "@connext/sdk";import { BigNumber } from "ethers";import { signer, sdkConfig } from "./config.js";const {sdkBase} = await create(sdkConfig);const signerAddress = await signer.getAddress();// xcall parametersconst originDomain = "1735353714";const destinationDomain = "1735356532";const originAsset = "0x7ea6eA49B0b0Ae9c5db7907d139D9Cd3439862a1";const amount = "1000000000000000000";const slippage = "10000";// Estimate the relayer feeconst relayerFee = (  await sdkBase.estimateRelayerFee({    originDomain,     destinationDomain  })).toString();// Prepare the xcall paramsconst xcallParams = {  origin: originDomain,           // send from Goerli  destination: destinationDomain, // to Mumbai  to: signerAddress,              // the address that should receive the funds on destination  asset: originAsset,             // address of the token contract  delegate: signerAddress,        // address allowed to execute transaction on destination side in addition to relayers  amount: amount,                 // amount of tokens to transfer  slippage: slippage,             // the maximum amount of slippage the user will accept in BPS (e.g. 30 = 0.3%)  callData: "0x",                 // empty calldata for a simple transfer (byte-encoded)  relayerFee: relayerFee,         // fee paid to relayers };// Approve the asset transfer if the current allowance is lower than the amount.// Necessary because funds will first be sent to the Connext contract in xcall.const approveTxReq = await sdkBase.approveIfNeeded(  originDomain,  originAsset,  amount)if (approveTxReq) {  const approveTxReceipt = await signer.sendTransaction(approveTxReq);  await approveTxReceipt.wait();}// Send the xcallconst xcallTxReq = await sdkBase.xcall(xcallParams);xcallTxReq.gasLimit = BigNumber.from("20000000"); const xcallTxReceipt = await signer.sendTransaction(xcallTxReq);console.log(xcallTxReceipt);await xcallTxReceipt.wait();

Most of the parameters are hardcoded in this example. For a detailed description of each parameter, see the SDK reference for xcall.

Information like asset addresses be found in the Deployments page.

4. Run it​

Fire off the cross-chain transfer!

npm run xtransfer

5. Track the xcall​

We can now use the transaction hash from the logged transaction receipt to track the status of this xcall.

»Tracking an xcall

After the transfer is status: Executed on the destination side, the transferred tokens should show up in the recipient wallet.