Channels

A channel lets Nuntium communicate with the world. By "the world" we mean anything that's not your particular application. For example: cellphone companies, email clients and twitter.

Kinds

A channel kind defines the way it communicates with the world. For instance, if a channel sends messages via SMTP we say that its kind is SMTP.

Directions

An incoming channel receives messages from "the world" into Nuntium so that later your application can receive them. In that way, it is incoming from the point of view of your application. These kind of messages are called Application Terminated messages because they terminate in your application.

An outgoing channel sends messages from Nuntium to "the world". Your application first sent those messages to Nuntium. In that way, it is outgoing from the point of view of your application. These kind of messages are called Application Originated messages because they are originated in your application.

A bi-directional channel is a channel that is both incoming and outgoing.

Examples of channel directions:

• Incoming: POP3
• Outgoing: SMTP
• Bi-directional: a channel that communicates with a cellphone company.

Protocols

You can have many outgoing channels in a Nuntium Application. A channel's protocol indicates which Application Originated messages are going to be sent via that channel.

For example, you might have an SMTP channel with a "mailto" protocol and a cellphone company channel with an "sms" protocol. If a message's "to" field is "mailto://some@email.com" it will be sent via the SMTP channel. If a message's "to" field is "sms://39569697" it will be sent via the cellphone company channel.

If you have more than one channel with the same protocol, routing logic is applied.

A message must always include a protocol in it's "to" field, otherwise a channel cannot be determined, even if you have a single outgoing channel.

Pausing and disabling

When you pause a channel, messages can still be routed to it but they will not be sent until you unpause it.

On the other hand, if you disable a channel then:

• Any queued messages in it will be routed to another enabled channel of the same protocol, if any
• No new messages will enqueued in it (the channel will never be a candidate of the routing process)

Channel Filter Phase

When an AO message arrives to Nuntium and has to be delivered through a channel, first a list of candidate channels is built. This list starts with all the account's channels and then:

• Only outgoing enabled channels are kept.
• Only channels for which the protocol is the same as the message's "to" field protocol are kept.
• Channels that have restrictions that don't match the message's custom attributes are discarded.

Channel Selection Strategy

Once a candidate channels list is built in the filter phase the application's strategy is applied:

• Broadcast: the message will be sent through all candidate channels.
• Single (Priority): the message will be sent through the channel with highest priority (smallest number). If there are more than one channel with highest priority, a random one will be chosen.

The strategy can be overriden by specifying a custom attribute in the message.