Inter-Transport Communication¶

Introduction¶

Inter-transport communication becomes necessary, when participants that connect to the bus using different transport mechanisms want to communicate.

This page describes how to setup participants for inter-transport communication using following scenario which is illustrated in the figure below:

• Participants reside in two separate processes
  • One process is an instance of the program inprocessAndSpread
    • There is one Informer in the process. It has two connectors
      • One connector for the Spread transport
      • One connector for the inprocess transport
    • There is one Listener in the process. It has two connectors
      • One connector for the Spread transport
      • One connector for the inprocess transport
  • The other process is an instance of the program spreadOnly
    • There is one Listener in the. It has a single connector for the Spread transport.

Inter-Transport Setup¶

There are two ways to attach multiple transports to participants:

1. Via configuration options (config file, environment variables, etc.)
2. Programmatically

These two alternatives are described below.

Via Configuration Options¶

When configured via the configuration mechanism, the multi-transport setup will have a global effect in the following sense: it will affect all participants in all processes which are not explicitly instantiated with a different set of connectors.

In addition to the Spread transport which is (currently) enabled by default, other transports can be enabled globally using a configuration file fragment like this:

[transport.inprocess]
enabled = 1

Programmatically (C++)¶

The set of transports used by individual participants or as a default by all newly created participants can be configured by modifying ParticipantConfig::Transport objects. These objects contain, among other things, an option which controls whether a particular transport is enabled. A modified ParticipantConfig object can be used in two ways:

• As new default participant configuration for the entire process
• As a configuration for one or more individual participants

These alternatives are discussed in the following sections.

Globally for a Process¶

The example programs inprocessAndSpread.cpp and spreadOnly.cpp implement the inter-transport setup described above by modifying the default participant configuration in the inprocessAndSpread process to include the inprocess transport.

The source code of both programs is available here:
source:trunk/cpp/core/examples/inter_transport/inprocessAndSpread.cpp
source:trunk/cpp/core/examples/inter_transport/spreadOnly.cpp

Locally for a Participant¶

In order to use a prepared ParticipantConfig object only locally instead of installing it as a global default, it can be passed to the following methods:

• Factory::createReader
• Factory::createListener
• Factory::createInformer

In each of these cases, the modified configuration options will only effect the participant created by the method call.