# Subscribing to a messaging channel

Chatlayer uses webhooks to allow external services to send messages to the platform.

In the app integrations world, this is performed by two functions: `performSubscribe` and `performUnsubscribe`.
The main goal of these two functions is to register and deregister the webhook which Chatlayer provides to the external service.
This webhook URL is available inside these functions.

## Perform subscribe

`performSubscribe` is responsible for registering a webhook to the external service. App integrations provide a value
inside `bundle.targetUrl` with the correct URL.

The following sample demonstrates what that could look like:


```javascript
module.exports = async (sdk, bundle) => {
    const body = {
        callback_url: bundle.targetUrl,
        bot_id: botId,
        bot_version: botVersion,
    };

    await sdk
        .request({
            url: 'https://myservice.com/webhooks',
            method: "POST",
            body,
        })
        .catch((err) => {
            throw new Error(`failed to register webhook: ${err.message}`);
        });
};
```

## Perform unsubscribe

`performUnsubscribe` is responsible for deregistering the previously registered webhook from the external service.

The following sample demonstrates what that could look like:


```javascript
module.exports = async (sdk, bundle) => {
    const body = {
        bot_id: botId,
        bot_version: botVersion,
    };

    await sdk
        .request({
            url: 'https://myservice.com/webhooks',
            method: "DELETE",
            body,
        })
        .catch((err) => {
            throw new Error(`failed to unregister webhook: ${err.message}`);
        });
};
```