How to resolve error in sending user data to USRP's SDRu transmitter function?

I'm trying to send user defined data over USRP board using SDRu Simulink blocks available. Following is the block diagram of my model:

Basically right now I'm trying to use the USRP board as a transceiver, hence the IP address of both Transmitter and Receiver are same. As of now, Transmitter is causing a problem regarding the input to it. Following is the error flashed:

I'm not really understanding this error. My input to the SDRu Transmitter a coloumn vector of fixed size 100. The reshape block is just transforming row vector to coloumn vector.

Also, if I remove the SDRu Transmitter block, the model runs perfectly, and I can see the variable recOut1 in the workspace. I hae gone through the QPSK example given in MATLAB examples. I really can't understand the source of this error. Can anyone shed some light on it?