Failed to list readers

[mbokil]

Your system information

• Operating system used: macOS Catalina
• pyscard version: 2.0.1
• Python version: 3.9.6

Please describe your issue in as much detail as possible:

Describe what you expected should happen.
Return list of readers
Describe what did happen.
I get an error message and script fails to run.
Traceback (most recent call last):
File "/usr/local/lib/python3.9/site-packages/smartcard/CardMonitoring.py", line 163, in run
currentcards = self.cardrequest.waitforcardevent()
File "/usr/local/lib/python3.9/site-packages/smartcard/CardRequest.py", line 72, in waitforcardevent
return self.pcsccardrequest.waitforcardevent()
File "/usr/local/lib/python3.9/site-packages/smartcard/pcsc/PCSCCardRequest.py", line 291, in waitforcardevent
readernames = self.getReaderNames()
File "/usr/local/lib/python3.9/site-packages/smartcard/pcsc/PCSCCardRequest.py", line 93, in getReaderNames
raise ListReadersException(hresult)
smartcard.Exceptions.ListReadersException: Failed to list readers: Service not available. (0x-7FEFFFE3)

Steps for reproducing this issue:

1. Create a simple class that consumes a ReaderObserver
2. Error occurs running script
3. Rolling back to pyscard 1.9.9 fixes the error for me

class DeviceObserver(ReaderObserver):
	"""A reader observer that is notified when card readers are added/removed"""

	def update(self, observable, actions):
		global key, log

		(addedreaders, removedreaders) = actions
		if addedreaders:
			log("Added readers", addedreaders)
			key = 1;
		if removedreaders:
			log("Removed readers", removedreaders)
			key = -2;

[LudovicRousseau]

First test your smart card reader is visible under macOS.
Follow https://ludovicrousseau.blogspot.com/2014/03/level-1-smart-card-support-on-mac-os-x.html

I guess that in your case NO reader was connected. Exact?

[mbokil]

Thanks for getting back to me. There is no problem with the reader. I think you missed my comment ,"Rolling back to pyscard 1.9.9 fixes the error for me." So if I uninstall the current version and install 1.9.9 the reader and code work fine. Seems to have broken after 2.x.

[LudovicRousseau]

Can you provide a complete sample code?

And really run pcsctest when you get the "Service not available" error.

[mbokil]

Sample code file attached as TXT. I extracted it from a larger project but tested it to ensure the error happens. Sometimes I don't get the error but if I stop the script and restart it I will often get the error.

MUSCLE PC/SC Lite Test Program

Testing SCardEstablishContext    : Command successful.
Testing SCardGetStatusChange
Please insert a working reader   : Command successful.
Testing SCardListReaders         : Command successful.
Reader 01: HID Global OMNIKEY 5022 Smart Card Reader
Enter the reader number          :

Added readers ['HID Global OMNIKEY 5022 Smart Card Reader']
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/smartcard/CardMonitoring.py", line 163, in run
    currentcards = self.cardrequest.waitforcardevent()
  File "/usr/local/lib/python3.9/site-packages/smartcard/CardRequest.py", line 72, in waitforcardevent
    return self.pcsccardrequest.waitforcardevent()
  File "/usr/local/lib/python3.9/site-packages/smartcard/pcsc/PCSCCardRequest.py", line 291, in waitforcardevent
    readernames = self.getReaderNames()
  File "/usr/local/lib/python3.9/site-packages/smartcard/pcsc/PCSCCardRequest.py", line 93, in getReaderNames
    raise ListReadersException(hresult)
smartcard.Exceptions.ListReadersException: Failed to list readers: Service not available. (0x-7FEFFFE3)

reader-test.txt

[LudovicRousseau]

What is the result of pcsctest after you get the "Service not available." error?

Did you removed the reader to get the error?

[mbokil]

The result of pcsctest is the same as before the error occurred. It shows command successful for all functions. I didn't remove the reader it has been plugged in all the time. Interestingly if I downgrade to version 1.9.9 the error goes away completely. For now as a workaround we have set the max version to 1.9.9 for mac users.

[LudovicRousseau]

I suspect the issue to be linked with db52d27

My problems:

• I don't understand why you get the "Service not available." error if pcsctest does not report the same error
• I can't reproduce the problem on my macOS (Big Sur)

[mbokil]

Was able to reproduce on Big Sur using the below profile.

macOS BigSur
Python 3.9.6
pyscard 2.0.1

Testing SCardEstablishContext : Command successful.
Testing SCardGetStatusChange
Please insert a working reader : Command successful.
Testing SCardListReaders : Command successful.
Reader 01: HID Global OMNIKEY 5022 Smart Card Reader

➜ scanner python3 reader-test.py
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/smartcard/CardMonitoring.py", line 163, in run
currentcards = self.cardrequest.waitforcardevent()
File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/smartcard/CardRequest.py", line 72, in waitforcardevent
return self.pcsccardrequest.waitforcardevent()
File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/smartcard/pcsc/PCSCCardRequest.py", line 291, in waitforcardevent
readernames = self.getReaderNames()
File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/smartcard/pcsc/PCSCCardRequest.py", line 93, in getReaderNames
raise ListReadersException(hresult)
smartcard.Exceptions.ListReadersException: Failed to list readers: Service not available. (0x-7FEFFFE3)

[LudovicRousseau]

I can reproduce the error.
I have to wait some time (like 30 seconds) before I get the error.

[LudovicRousseau]

Try with this patch:

--- a/smartcard/pcsc/PCSCContext.py
+++ b/smartcard/pcsc/PCSCContext.py
@@ -52,7 +52,8 @@ class PCSCContext(object):
     def __init__(self):
         PCSCContext.mutex.acquire()
         try:
-            self.renewContext()
+            if not PCSCContext.instance:
+                self.renewContext()
         finally:
             PCSCContext.mutex.release()

[mbokil]

@LudovicRousseau I applied the patch and rebuild using ➜ pyscard-master python3 setup.py build_ext install. Confirming the error is gone now. Thanks!

[LudovicRousseau]

Thanks for the feedback
Fixed in da43dda