I don't know whether the 4.2 and 4.3 libraries are compatible. But from what you describe it looks like not.
In that case you need to bundle the external jbossall-client.jar in your application and configure the classloader to prevent loading the local API classes. See classloading wiki
But as there is a communication timeout, are you sure you have used the correct ports, maybe you set the port with jnp....host:1099 explicit.