Arduino problem with gPredict and rotctld

Hi, I am trying to make satellite tracker. I am new to raspberry pi as well. I have installed gpredict and hamlib in raspberry pi. currently I am trying to send azimuth and elevation value from gpredict to arduino via usb. I tried ‘rotctld -r /dev/ttyUSB0 -s 9600’ and I am trying to read the value by just Serial.read(); in the arduino. But its not working. Can anyone help me what should I do? I am new to this project.