Backend

LAST EDIT Jun 10 2021

For the average Stream integration, the majority of the the development work focuses on code that executes in the client. The React, React Native, Swift, Kotlin or Flutter SDKs connect to the chat API directly from the client. However, some tasks must be executed from the server for safety

The chat API has some features that client side code can manage in specific cases but usually shouldn't. While these features can be initiated with client side code, we recommend managing them server side instead unless you are certain that you need to manage them from the client side for your specific use case.

The backend has full access to the chat API.

This quick start covers the basics of a backend integration. If we don't have an SDK for your favorite language be sure to review the REST documentation.

Generating user tokens

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The backend creates a token for a user. You hand that token to the client side during login or registration. This token allows the client side to connect to the chat API for that user. Stream's permission system does the heavy work of determining which actions are valid for the user, so the backend just needs enough logic to provide a token to give the client side access to a specific user.

The following code shows how to instantiate a client and create a token for a user on the server:

You can also generate tokens that expire after a certain time. The tokens & authentication section explains this in detail.

Syncing users

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When a user starts a chat conversation with another user both users need to be present in Stream's user storage. So you'll want to make sure that users are synced in advance. The update users endpoint allows you to update 100 users at once, an example is shown below:

Note that user roles can only be changed server side. The role you assign to a user impacts their permissions and which actions they can take on a channel.

Syncing Channels

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You can create channels client side, but for many applications you'll want to restrict the creation of channels to the backend. Especially if a chat is related to a certain object in your database. One example is building a livestream chat like Twitch. You'll want to create a channel for each Stream and set the channel creator to the owner of the Stream. The example below shows how to create a channel and specify the moderators:

You can also add a message on the channel when updating it. It's quite common for chat apps to show messages like: "Jack invited John to the channel", or "Kate changed the color of the channel to green".

Adding Members or Moderators

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The backend SDKs also make it easy to add or remove members from a channel. The example below shows how to add and remove members:

Sending Messages

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It's quite common that certain actions in your application trigger a message to be send. If a new user joins an app some chat apps will notify you that your contact joined the app. The example below shows how to send a message from the backend. It's the same syntax as you use client side, but specifying which user is sending the message is required: