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## Resource: wix-realtime-backend



## Article: Introduction

## Article Link: https://dev.wix.com/docs/velo/velo-only-apis/wix-realtime-backend/introduction.md

## Article Content:

# Introduction
> **Note**: This API is not supported in [Wix Blocks](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/wix-blocks/about-wix-blocks.md).

 Using the Realtime API you can create channels and channel resources where messages
 can be published. Site visitors who subscribe to a channel receive the published
 messages published to that channel. When a message is received you can handle the message any
 way you choose, such as displaying the contents of the message or changing the state
 of page elements depending on the contents of the message. You can also manage the
 permissions of who can read from specific channels.

 The `wix-realtime-backend` module is used in conjunction with the 
 [`wix-realtime-frontend`](wix-realtime-frontend.html) module.

 Get hands-on experience with the Realtime API on our [Hello Realtime](https://dev.wix.com/docs/coding-examples/getting-started/hello-world/hello-realtime.md) example page. 

 Typical uses of the Realtime API include implementing a messaging system or
 as an alternative to using a polling mechanism.

 The Realtime API uses the following terminology:

 + **Channel**: A specific channel on which messages are published. Each channel
   has a unique name. Site visitors can subscribe to a channel to receive the 
   messages that are published on it. When site visitors subscribe to a channel, they do not 
   receive messages published to a resource on that same channel.
 + **Channel resource**: A subchannel on which messages are published. Subchannels
   can share a name with a channel and other subchannels, but they have a unique
   resource ID. When site visitors subscribe to a channel resource, they do not 
   receive messages published to that same channel without a specified resource.
   Channel resources inherit their parent channel's permissions, unless specified
   otherwise.
 + **Message**: A message published on a channel or channel resource. A message can
   be of any type, such as a string, number, or object. Channel subscribers receive
   the messages published on the channel.
 + **Publish**: Sending a message over a channel or channel resource.
 + **Subscribe**: A site visitor subscribes to receive the messages published on a 
   channel or channel resource.
 + **Permissions router**: The permissions router is used to define the permissions
   you want to grant to subscribers on channels and channel resources.
 + **Permissions handler**: Handles a permissions check for a specific user on a 
   specific channel or channel resource.
 
 For a tutorial on using the Realtime API, see 
 [Sending Messages with the Realtime API](https://support.wix.com/en/article/velo-tutorial-sending-messages-with-the-realtime-api).

 To use the Realtime API in the backend, import `wixRealtimeBackend` from the `wix-realtime-backend` module:

   ```javascript
   import wixRealtimeBackend from 'wix-realtime-backend';
   ```