I tried the Request-Reply-Example which is in the C++ example folder of RTI 5.1.0.
If I use the Requester in a command window (Ubuntu 12.04) and the Replier in another command windows on the same machine,
the Requester sporadically (can be the second time or the 20. time I send a request) doesn't get the data from the Replier. But the Replier gets the request and says that he replied (in the command window).