Client runtime support is provided in libraries that you use when building and running Message Queue clients. You can think of the client runtime as the part of the Message Queue service that enables the client. For example, when client code makes an API call to send a message, code in these libraries is invoked that packages the message bits appropriately for the protocol that will be used to relay the message to a physical destination on the broker.
A JMS provider is only required to support Java clients; however, as Figure 1–6 shows, a Message Queue client can use either the Java API or a proprietary C API to send or receive a message. These interfaces are implemented in Java or C runtime libraries, which do the actual work of creating connections to the broker and packaging the bits appropriately for the connection service being used.
The C client runtime supplies C clients with the functions and structures needed to interact with the broker. It supports a procedural version of the JMS programming model. C clients cannot use JNDI to access administered objects, but can create connection factories and destinations programmatically. Message Queue provides the C API to enable legacy C and C++ applications to participate in JMS-based messaging.
There are a number of differences in the functionality provided by these two APIs; these are documented in Java and C Clients.
It is important to remember that the JMS specification is a standard for Java clients only. C support is specific to the Message Queue provider and should not be used in client applications that you plan to port to other providers.
SOAP (Simple Object Access Protocol) allows the exchange of structured data between two peers in a distributed environment. The data exchanged is specified by an XML schema. SOAP message delivery is limited to using the point-to-point domain and does not by itself guarantee reliability.
However, Message Queue Java clients are able to send and receive SOAP messages, encapsulated as JMS messages. By encapsulating a SOAP message in a JMS message and delivering it using the broker, you can take advantage of full featured Message Queue messaging, which guarantees reliable delivery and also allows you to use the publish/subscribe domain. Message Queue provides utility routines that a message producer can use to encapsulate a SOAP message as a JMS message and that a message consumer can use to extract a SOAP message from the JMS message. Message Queue also provides XML schema validation of the encapsulated XML message.
Working with SOAP Messages gives you a more detailed view of SOAP message processing.