Messages

Veramo can communicate with other systems using it's messaging system. The messaging system is comprised of a Message Type, a MessageHandler interface, a MessageHandler plugin that accepts multiple message parsers plugins that implement AbstractMessageHandler You can create custom message handling plugins to add new message types for your agent.

Handling Messages

A message can be introduced to the Agent in a number of ways including via REST endpoint if you are using Veramo Server or by scanning a QR code if you are using Veramo Client on mobile. The MessageHandler's main responsibility is to try to convert incoming messages to the correct data model so they can be understood by Veramo and optionally be stored for later use.

When you bootstrap a Veramo Agent you will have something that looks like this:

const agent = new Agent({
  plugins: [
    new MessageHandler({
      messageHandlers: [
        new DIDCommMessageHandler(),
        new JwtMessageHandler(),
        new W3cMessageHandler(),
        new SdrMessageHandler(),
      ],
    }),
  ],
})

The MessageHandler handler plugin is instantiated with message parsers. These parsers implement the AbstractMessageHandler interface. The MessageHandler plugin adds a handleMessage method to the agent and can be invoked by calling agent.handleMessage(). Regardless of what configuration your agent is in this method is the entry-point for all messages.

When the MessageHandler is instantiated it creates a chain of message parsers (AbstractMessageHandler) in the exact order specified in the configuration.

The above example would look like this:

Each parser will try to read the message and return a message object by examining the payload/type and deciding if it can do the job or if it should pass it onto the next parser in the chain if one exists. Once a message can be interpreted a message object is constructed, it is returned and optionally saved.

You can learn more about how each message handler parses messages in the next section.