# Lightning Message Service Methods for Lightning Experience

## Usage

These three methods allow your CTI implementation to communicate with other Visualforce, Aura, and Lightning components that also use the Lightning Message Service. The `subscribe` method attaches a listener function to a specified Lightning Message Channel. The `publish` method lets you send a message on a Lightning Message Channel. The `unsubscribe` method lets you remove listener functions you added with the subscribe method.

These methods are available in API version 47.0 or later.

:::note
These methods can be used only with Lightning Experience. They can be used in iFrame and Visualforce components.
:::

## Syntax

The `subscribe` method allows you to attach a listener function to a specified Lightning Message Channel. Lightning Message Service calls your listener function with the message that a component sends.

```javascript
var SAMPLEMC = "SAMPLEMC__c";
var SAMPLEMC_SUBSCRIPTION = null; 
sforce.opencti.subscribe({channelName: SAMPLEMC, listener: onPublishMessage, callback: subscribeSampleMCCallback}); 

```

## Arguments for `subscribe`

| Name          | Type     | Description                                                                    |
| ------------- | -------- | ------------------------------------------------------------------------------ |
| `channelName` | string   | The name of the Message Channel that you can subscribe to.                     |
| `listener`    | function | JavaScript method that’s called when a message is sent on the Message Channel. |
| `callback`    | function | JavaScript method that’s executed when the API method call is completed.       |

## Arguments for `unsubscribe`

| Name           | Type     | Description                                                              |
| -------------- | -------- | ------------------------------------------------------------------------ |
| `subscription` | object   | The subscription from which you can remove the listener function.        |
| `callback`     | function | JavaScript method that’s executed when the API method call is completed. |

## Arguments for `publish`

| Name          | Type     | Description                                                              |
| ------------- | -------- | ------------------------------------------------------------------------ |
| `channelName` | string   | The name of the Message Channel that you can subscribe to.               |
| `message`     | object   | Serializable JSON object that is sent on the Message Channel.            |
| `callback`    | function | JavaScript method that’s executed when the API method call is completed. |