Interfacing to Linuxcncrsh from another PC

Hi guys,

Would like to get some pointer and howto for linuxcncrsh.

Background: 
I installed linuxcnc on orangepi using this allwincnc.github.io/
Machine is actually a pick and place machine rather than machining machine. Configured linuxcnc to control 4 axis (XYZA, I declare A as linear axis eventhough it's actually a rotation axis, and just record the required number to rotate it to where I want it to go)
Everything moved, and runs as expected using gcode.

I need to control this machine from another computer with a GUI to do an automatic pick and place based on a vision system feedback on what object is detected.

I am currently using linuxcncrsh to get the control running and communicate through network using telnet protocol. My code in the GUI wil call a gcode program in the orangepi to do the robot movement, to pick and place it object in the correct station. Currently program is running fine as long as there is no error (e.g. vacuum failed to pick up object, robot moved in the wrong direction and crash, some object blocking the insertion path, etc)

My problem:
My program is fairly blind. The way I talk to linuxcncrsh and check if the robot is moving correctly is by detecting the program status. If the program is in paused state, it is indicating that there is error, e.g. vacuum switch is not detecting the object being picked up. In the gcode program I will be detecting all the required sensor detection using M66  and checking #5399 for required pin, and if there is timeout or the pin did not go as expected I will pause the program. The problem is I would rather have direct checking of the input pin in the linuxcnc so I can have a better error explanation rather than just a robot error (current code will throw a robot error if it sees the program status as paused). 

My question :
What wil be the easiest way to talk to linuxcnc to check the pin status ? 

Thanks for any pointer....
 

I tried get error, get operator_text and get operator_display, all of them always reply with ok, no matter what print or debug msg i tried to put in the g code. Btw i used linuxcncrsh in the background while axis is running to have visual feedback for me to confirm that gcode is running and axes are moving properly. So it could be causing the get error etc to not seeing the text. Will start and try to run only linuxcncrsh.

So... running linuxcncrsh stand alone, i.e. without axis interface allows me to send text back to PC in a form of operator_display. Put a (debug, things to send to pc) in the gcode and pausing the program allows the pc to interact with the linuxcncrsh and have some sort of idea of which gcode line is running. Coupled with set open, set run programline, and set abort, it's good enough for me to pretty much be able to interact and check the pin status. 

Take note, the operator_display is buffered, and if it's not cleared, it will display the earlier operator_display and not the latest one.

Another thread for reference to read or set hal pin value :
www.forum.linuxcnc.org/38-general-linuxc...l-pin-while-in-gcode
forum.linuxcnc.org/47-hal-examples/33270...n-from-gcode?start=0