Messaging is intended to enable a wide variety of computers to exchange information. One of the main benefits of messaging is to 'decouple' a sending application from a receiving application. This decoupling provides a very powerful abstraction, enabling the exchange of information to be independent of manufacturer, application, operating system or connectivity reliability.
Traditionally, messaging is between large computers and a server. However, with the advent of Java messaging implementations, now a new class of device interoperates with the messaging infrastructure. This provides opportunities for an enterprise to broaden the reach of its networks.
Along with the transmission of simple messages, messaging is useful for transactional updates, or where intermediate data updates or data ordering is required. Messages containing the complete update can be sent to a server, where transaction managers can coordinate the update of multiple resources. Messaging can also be paired with synchronization technology, such that transactions are sent by messages, and the resulting database updates distributed back to the client through synchronization.
Messaging also can be used effectively in a disconnected environment (areas where connectivity is not reliable), since a local queue manager is available to contain messages until the connection to the server infrastructure is reestablished. After the connection is available, the queued messages are transferred to the messaging server for further action.
Messaging, irrespective of the particular product or product group, is separated into two main categories:
- Point-to-point messaging
- Publish and Subscribe messaging
To take full advantage of the messaging capabilities of Lotus® Expeditor, it is crucial to understand the differences in these two messaging types.
Publish and subscribe messaging
Publish and subscribe is a style of messaging in which applications (subscribers) register interest in a particular subject (known as a topic) with an intermediary (a broker). The broker then compares those subscription topics to the topics of messages sent by other applications (publishers) and forwards messages to those subscribers where a match is made.
In contrast with publish/subscribe messaging, which allows a publisher to send a message to multiple subscribers, point-to-point messaging is designed to allow communication from one message producer to one message consumer.
Messaging protocols: XPD622
The micro broker supports two types of messaging for communicating with its clients and with other brokers. The first uses messages built according to the MQTT protocol (details of which are publicly available), while the second uses the Java Messaging Service (JMS) API specification.
The micro broker implements the server half of the MQTT protocol. This allows MQTT clients to connect as publishers and subscribers.
WebSphere MQ Everyplace: XPD622
WebSphere® MQ Everyplace® (MQe) is a member of the IBM® WebSphere MQ family of business messaging products. It exchanges messages with various applications, providing once and once-only assured delivery leveraging the point to point message paradigm.
Lotus Expeditor micro broker overview
The Lotus Expeditor micro broker component is a small message broker that provides a messaging fabric for integrating various parts of a solution. It is particularly aimed at resource limited environments such as those that may be found in “edge of network” devices running applications that measure and control physical properties (temperature and fluid flow, for example) using sensors and actuators. A message broker ensures that messages arrive at the correct destination and are transformed to the format required by each destination.
WebSphere MQ Everyplace and micro broker comparison: XPD622
While MQe and micro broker products are similar in that they provide embedded messaging capabilities; their specific set of features might make a better choice for certain client applications.
Parent topic: Developing messaging applications: XPD622