Channels

Each application can have one channel or many, and each client can choose which channels it subscribes to.

Channels provide:

• A way of filtering data For example, in a chat application there may be a channel for people who want to discuss ‘dogs’
• A way of controlling access to different streams of information. For example, a project management application would want to authorize people to get updates about ‘secret-projectX’

We strongly recommend that channels are used to filter your data and that it is not achieved using events. This is because all events published to a channel are sent to all subscribers, regardless of their event binding.

Channels do not need to be explicitly created, and are instantiated on client demand. This means that creating a channel is easy. Just tell a client to subscribe to it.

∞ Channel Types

There are 4 types of channels at the moment:

• Public channels can be subscribed to by anyone who knows their name
• Private channels should have a private- prefix. They introduce a mechanism which lets your server control access to the data you are broadcasting
• Private encrypted channels should have a private-encrypted- prefix. They extend the authorization mechanism of private channels, adding encryption of the data payloads so that not even Pusher can get access to it without authorization.
• Presence channels should have a presence- prefix and are an extension of private channels. They let you ‘register’ user information on subscription, and let other members of the channel know who’s online
• Cache channels remembers last published message and delivers it to clients when they subscribe. Cache channel is available in public, private, and private-encrypted modes.

∞ Channel Naming Conventions

Channel names may contain a maximum of 164 characters. This limit includes channel prefixes (i.e. private- and presence- are included in the character count).

Channel names should only include lower and uppercase letters, numbers and the following punctuation _ - = @ , . ; As an example this is a valid channel name:

foo-bar_1234@=,.;

# is a reserved character for internal use by Pusher Channels. Applications can’t create channel names containing #.

∞ Accessing channels

If a channel has been subscribed to already it is possible to access channels by name, through the pusher.channel function:

var channel = pusher.channel(channelName);

∞ channelNameString Required

The name of the channel to retrieve