(Ruby) 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 Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

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

scard = Chilkat::CkSCard.new()

# First establish a context to the PC/SC Resource Manager
success = scard.EstablishContext("user")
if (success == false)
    print scard.lastErrorText() + "\n";
    exit
end

# 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.new()
success = scard.FindSmartcards(json)
if (success == false)
    print scard.lastErrorText() + "\n";
    exit
end

# 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() + "\n";
print " " + "\n";

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

sbState = Chilkat::CkStringBuilder.new()

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." + "\n";
    else
        print name + " does not have a smart card inserted." + "\n";
    end

    i = i + 1
end
print " " + "\n";

# 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.new()
success = scard.ListReaders(stReaders)
if (success == false)
    print scard.lastErrorText() + "\n";
    exit
end

# Show the reader names..
numReaders = stReaders.get_Count()
i = 0
while i < numReaders
    print i.to_s() + ": " + stReaders.stringAt(i) + "\n";
    i = i + 1
end

# 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.new()
success = scard.GetStatusChange(30000,stReaders,json2)
if (success == false)
    print scard.lastErrorText() + "\n";
    exit
end

print " " + "\n";

# Let's see what happened...
json2.put_EmitCompact(false)
print json2.emit() + "\n";
print " " + "\n";

# 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: " + numChanged.to_s() + "\n";

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: " + "\n";
        print "    reader name: " + name + "\n";
        print "    new state: " + state + "\n";

        # 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 + "\n";
        end

    end

    i = i + 1
end

# 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() + "\n";
end