Lua Requires Chilkat v9.5.0.87+

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

See more SCard Examples

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. Lua

local chilkat = require("chilkat")

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

local scard = chilkat.SCard.new()

-- First establish a context to the PC/SC Resource Manager
local success = scard:establish_context("user")
if not success then
    print(scard.last_error_text)
    return
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.
local json = chilkat.JsonObject.new()
success = scard:find_smartcards(json)
if not success then
    print(scard.last_error_text)
    return
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.emit_compact = false
print(json:emit())
print(" ")

-- We can iterate over the JSON to find the readers with a smart card already inserted..
local name = ""
local sbState = chilkat.StringBuilder.new()

local i = 0
local count_i = json:size_of_array("reader")
while i < count_i do
    json.i = i
    name = json:string_of("reader[i].name")

    sbState:clear()
    json:string_of_sb("reader[i].state", sbState)

    if sbState:contains("present", true) then
        print(name .. " has a smart card inserted.")
    else
        print(name .. " does not have a smart card inserted.")
    end

    i = i + 1
end

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.
local stReaders = chilkat.StringTable.new()
success = scard:list_readers(stReaders)
if not success then
    print(scard.last_error_text)
    return
end

-- Show the reader names..
local numReaders = stReaders.count
i = 0
while i < numReaders do
    print(i .. ": " .. stReaders:string_at(i))
    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.
local json2 = chilkat.JsonObject.new()
success = scard:get_status_change(30000, stReaders, json2)
if not success then
    print(scard.last_error_text)
    return
end

print(" ")

-- Let's see what happened...
json2.emit_compact = 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...
local changed = false
local state = ""
local atr = ""

local numChanged = json2:int_of("numChanged")
print("number of readers with a changed state: " .. numChanged)

i = 0
count_i = json2:size_of_array("reader")
while i < count_i do
    json2.i = i
    changed = json2:bool_of("reader[i].changed")
    if changed then
        name = json2:string_of("reader[i].name")
        state = json2:string_of("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:has_member("reader[i].atr") then
            atr = json2:string_of("reader[i].atr")
            print("    ATR of card inserted into this reader: " .. atr)
        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:release_context()
if not success then
    print(scard.last_error_text)
end