(CkPython) PC/SC Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)

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Demonstrates how to synchronously wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader.

Note: This functionality was introduced in Chilkat v9.5.0.87.

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

scard = chilkat.CkSCard()

# First establish a context to the PC/SC Resource Manager
success = scard.EstablishContext("user")
if (success == False):
    print(scard.lastErrorText())
    sys.exit()

# First we'll examine the state of all connected readers to see which have smartcards already inserted..
# Get JSON containing information about the smartcards currently inserted into readers.
# This also includes information about USB security tokens.
json = chilkat.CkJsonObject()
success = scard.FindSmartcards(json)
if (success == False):
    print(scard.lastErrorText())
    sys.exit()

# When writing this example, I have 3 smart card readers plugged into my system.
# One of them has a smart card inserted.
# Here's the JSON returned by FindSmartcards...

# {
#   "reader": [
#     {
#       "name": "Alcor Micro USB Smart Card Reader 0",
#       "state": "empty"
#     },
#     {
#       "name": "Generic Smart Card Reader Interface 0",
#       "state": "present",
#       "vendorName": "Generic",
#       "serialNumber": "3230303730383138303030303030303030",
#       "systemName": "Generic Smart Card Reader Interface 0",
#       "card": {
#         "atr": "3BFC180000813180459067464A00641606F2727E00E0",
#         "windows": {
#           "miniDriver": "tagliov70px.dll",
#           "cryptoProvider": "Microsoft Base Smart Card Crypto Provider",
#           "keyStorageProvider": "Microsoft Smart Card Key Storage Provider"
#         }
#       }
#     },
#     {
#       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
#       "state": "empty"
#     }
#   ]
# }

json.put_EmitCompact(False)
print(json.emit())
print(" ")

# We can iterate over the JSON to find the readers with a smart card already inserted..

sbState = chilkat.CkStringBuilder()

i = 0
count_i = json.SizeOfArray("reader")
while i < count_i :
    json.put_I(i)
    name = json.stringOf("reader[i].name")

    sbState.Clear()
    json.StringOfSb("reader[i].state",sbState)

    if (sbState.Contains("present",True) == True):
        print(name + " has a smart card inserted.")
    else:
        print(name + " does not have a smart card inserted.")

    i = i + 1

print(" ")

# Now let's begin the code to wait for a change (where a smart card gets inserted or removed)

# Get the list of all readers.
stReaders = chilkat.CkStringTable()
success = scard.ListReaders(stReaders)
if (success == False):
    print(scard.lastErrorText())
    sys.exit()

# Show the reader names..
numReaders = stReaders.get_Count()
i = 0
while i < numReaders :
    print(str(i) + ": " + stReaders.stringAt(i))
    i = i + 1

# Sample output from the above loop.
# 0: Alcor Micro USB Smart Card Reader 0
# 1: Generic Smart Card Reader Interface 0
# 2: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
# 

# Synchronously wait 30 seconds for a card to be inserted or removed from any of the above readers.
json2 = chilkat.CkJsonObject()
success = scard.GetStatusChange(30000,stReaders,json2)
if (success == False):
    print(scard.lastErrorText())
    sys.exit()

print(" ")

# Let's see what happened...
json2.put_EmitCompact(False)
print(json2.emit())
print(" ")

# This is what json2 contains.
# A card was inserted into the reader named "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
# The "numChanged" indicates that one reader's status changed.  
# The "changed":true indicates the reader that changed.   The state is now "present".

# {
#   "numChanged": 1,
#   "reader": [
#     {
#       "name": "Alcor Micro USB Smart Card Reader 0",
#       "changed": false,
#       "state": "empty"
#     },
#     {
#       "name": "Generic Smart Card Reader Interface 0",
#       "changed": false,
#       "state": "present",
#       "atr": "3BFC180000813180459067464A00641606F2727E00E0"
#     },
#     {
#       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
#       "changed": true,
#       "state": "present",
#       "atr": "3BDF96FF8131FE455A018048494443313158587300011B09"
#     }
#   ]
# }

# Find the reader that changed...

numChanged = json2.IntOf("numChanged")
print("number of readers with a changed state: " + str(numChanged))

i = 0
count_i = json2.SizeOfArray("reader")
while i < count_i :
    json2.put_I(i)
    changed = json2.BoolOf("reader[i].changed")
    if (changed == True):
        name = json2.stringOf("reader[i].name")
        state = json2.stringOf("reader[i].state")

        print("Changed: ")
        print("    reader name: " + name)
        print("    new state: " + state)

        # If a card is now in this reader, we should have the ATR of the card..
        if (json2.HasMember("reader[i].atr") == True):
            atr = json2.stringOf("reader[i].atr")
            print("    ATR of card inserted into this reader: " + atr)

    i = i + 1

# The output from the above loop:

# number of readers with a changed state: 1
# Changed: 
#     reader name: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
#     new state: present
#     ATR of card inserted into this reader: 3BDF96FF8131FE455A018048494443313158587300011B09

# Applications should always release the context when finished.
success = scard.ReleaseContext()
if (success == False):
    print(scard.lastErrorText())