BACnet ReadProperty command
Usage: bacrp device-instance object-type object-instance property [index]

device-instance:
BACnet Device Object Instance number that you are trying to communicate to.
This number will be used to try and bind with the device using Who-Is and I-Am services.
For example, if you were reading Device Object 123, the device-instance would be 123.

object-type:
The object type is the integer value of the object that you are reading.
For example if you were reading Analog Output 2, the object-type would be 1.

object-instance:
This is the object instance number of the object that you are reading.
For example, if you were reading Analog Output 2, the object-instance would be 2.

property:
The property is an integer value of the property you are reading.
For example, if you were reading the Present Value property, use 85 as the property.

index:
This integer parameter is the index number of an array.
If the property is an array, individual elements can be read.
If this parameter is missing and the property is an array, the entire array will be read.

Examples:
If you want read the Present-Value of Analog Output 101 in Device 123, you could send the following command:
bacrp 123 1 101 85

If you want read the Priority-Array of Analog Output 101 in Device 123, you could send the following command:
bacrp 123 1 101 87