HornetQ requires several jars on the Client Classpath depending on whether the client uses HornetQ Core API, JMS, and JNDI.
All the jars mentioned here can be found in the lib directory of the HornetQ distribution. Be sure you only use the jars from the correct version of the release, you must not mix and match versions of jars from different HornetQ versions. Mixing and matching different jar versions may cause subtle errors and failures to occur.
If you are using just a pure HornetQ Core client (i.e. no JMS) then you need hornetq-core-client.jar, hornetq-transports.jar and netty.jar on your client classpath.
If you are using JMS on the client side, then you will also need to include hornetq-jms-client.jar and jboss-jms-api.jar.
jboss-jms-api.jar just contains Java EE API interface classes needed for the javax.jms.* classes. If you already have a jar with these interface classes on your classpath, you will not need it.