How to do two way communication using xbee

I am facing a problem related to xbee and requires your help. Actually I am making a project “Home automation using xbee”.
In this project I want to use pir sensor,fire sensor and receive its output through xbee at controller(pic 16877A) side to the Xbee at user end and controlling the ac devices accordingly from computer. But my main problem is that I am not able to configure my xbee for both receiving and transmitting simultaneously. One of my xbee is acting like receiver and other is acting like transmitter at a time. Since I require my xbee to obtain signals from sensors at controller side to the pc and send commands from my pc to the controller and control devices and therefore seeking your help to configure xbee for transmission and reception simultaneously.

Do I need to use 4 xbee i.e 2 at controller side for transmitting and receiving respectively and two at pc end for receiving and transmitting or it is possible using 2 xbee only i.e 1 at controller side and other one at pc side for transmitting and receiving respectively, please tell me the required configuration.
My xbee model is:- XB24-B
Thanks in advance.

Step through this getting started guide, it will walk you through getting the radios configured for two-way communication:

does anyone have an answer that works?

What you are working with is what is called the XBee ZB or Zigbee enabled modules. They support Point to point, point to multi-point and Mesh network typologies. This means that you can have two or more remote modules sending data to one module. You can also have that one module send data to all remote modules or just one. It is a matter of the addressing functions you use on the radio.

If you are using the XBee’s Analog ti Digital convert, then you need to put the module that is connected to the PC receiving the ADC data in API mode.

While the following article is written for the XBee modules, it will give you an idea of how it is done.