add listening mode to the reader

remote-reader/app/src/main/java/com/vsmartcard/remotesmartcardreader/app/MainActivity.java

@@ -198,11 +198,12 @@ public class MainActivity extends AppCompatActivity implements NfcAdapter.Reader
     }
 
     private void vpcdConnect(SCReader scReader) {
-        SharedPreferences SP = PreferenceManager.getDefaultSharedPreferences(this);
+        final SharedPreferences SP = PreferenceManager.getDefaultSharedPreferences(this);
-        int port = Integer.parseInt(SP.getString("port", Integer.toString(VPCDWorker.DEFAULT_PORT)));
+        final int port = Integer.parseInt(SP.getString("port", Integer.toString(VPCDWorker.DEFAULT_PORT)));
-        String hostname = SP.getString("hostname", VPCDWorker.DEFAULT_HOSTNAME);
+        final String hostname = SP.getString("hostname", VPCDWorker.DEFAULT_HOSTNAME);
+        final boolean listen = SP.getBoolean("listen", VPCDWorker.DEFAULT_LISTEN);
         vpcdTest = new VPCDWorker();
-        vpcdTest.execute(new VPCDWorker.VPCDWorkerParams(hostname, port, scReader));
+        vpcdTest.execute(new VPCDWorker.VPCDWorkerParams(hostname, port, scReader, listen));
     }
 
     private void vpcdDisconnect() {

remote-reader/app/src/main/java/com/vsmartcard/remotesmartcardreader/app/VPCDWorker.java

@@ -29,8 +29,17 @@ import com.vsmartcard.remotesmartcardreader.app.screaders.SCReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.net.Inet4Address;
 import java.net.InetAddress;
+import java.net.InterfaceAddress;
+import java.net.NetworkInterface;
+import java.net.ServerSocket;
 import java.net.Socket;
+import java.net.SocketTimeoutException;
+import java.util.Enumeration;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 class VPCDWorker extends AsyncTask<VPCDWorker.VPCDWorkerParams, Void, Void> {
 
@@ -38,18 +47,22 @@ class VPCDWorker extends AsyncTask<VPCDWorker.VPCDWorkerParams, Void, Void> {
         final String hostname;
         final int port;
         final SCReader reader;
-        VPCDWorkerParams(String hostname, int port, SCReader reader) {
+        final boolean listen;
+        VPCDWorkerParams(String hostname, int port, SCReader reader, boolean listen) {
             this.hostname = hostname;
             this.port = port;
             this.reader = reader;
+            this.listen = listen;
         }
     }
 
     public static final int DEFAULT_PORT = 35963;
     // default URI when used in emulator
     public static final String DEFAULT_HOSTNAME = "10.0.2.2";
+    public static final boolean DEFAULT_LISTEN = false;
 
     private SCReader reader;
+    private ServerSocket listenSocket;
     private Socket socket;
     private InputStream inputStream;
     private OutputStream outputStream;
@@ -75,15 +88,22 @@ class VPCDWorker extends AsyncTask<VPCDWorker.VPCDWorkerParams, Void, Void> {
     public Void doInBackground(VPCDWorkerParams... params) {
         try {
             reader = params[0].reader;
-            Log.i(this.getClass().getName(), "Connecting to " + params[0].hostname + ":" + Integer.toString(params[0].port) + "...");
+            vpcdConnection(params[0]);
-            vpcdConnect(params[0].hostname, params[0].port);
-            Log.i(this.getClass().getName(), "Connected to VPCD");
 
             while (!isCancelled()) {
+                vpcdAccept();
                 byte[] out = null;
                 byte[] in = receiveFromVPCD();
-                if (in == null)
+                if (in == null) {
-                    break;
+                    if (listenSocket == null) {
+                        Log.i(this.getClass().getName(), "End of stream, finishing");
+                        break;
+                    } else {
+                        Log.i(this.getClass().getName(), "End of stream, closing connection");
+                        vpcdCloseClient();
+                        continue; // back to accept
+                    }
+                }
 
                 if (in.length == VPCD_CTRL_LEN) {
                     switch (in[0]) {
@@ -169,7 +189,79 @@ class VPCDWorker extends AsyncTask<VPCDWorker.VPCDWorkerParams, Void, Void> {
         outputStream.flush();
     }
 
+    private void vpcdConnection(VPCDWorkerParams params) throws IOException {
+        if (params.listen){
+            vpcdListen(params.port);
+            return;
+        }
+
+        Log.i(this.getClass().getName(), "Connecting to " + params.hostname + ":" + Integer.toString(params.port) + "...");
+        vpcdConnect(params.hostname, params.port);
+        Log.i(this.getClass().getName(), "Connected to VPCD");
+    }
+
+    private void vpcdListen(int port) throws IOException {
+        listenSocket = new ServerSocket(port);
+
+        final List<String> ifaceAddresses = new LinkedList<>();
+        final Enumeration<NetworkInterface> ifaces = NetworkInterface.getNetworkInterfaces();
+        while(ifaces.hasMoreElements()){
+            final NetworkInterface iface = ifaces.nextElement();
+            if (!iface.isUp() || iface.isLoopback() || iface.isVirtual()) {
+                continue;
+            }
+            for(InterfaceAddress addr : iface.getInterfaceAddresses()){
+                final InetAddress inetAddr = addr.getAddress();
+                ifaceAddresses.add(inetAddr.getHostAddress());
+            }
+        }
+
+        Log.i(this.getClass().getName(), "Listening on port " + port + ". Local addresses: " + join(", ", ifaceAddresses));
+    }
+
+    private void vpcdAccept() throws IOException {
+        if(listenSocket == null){
+            return;
+        }
+
+        if (socket != null){
+            return;  // Already accepted, only one client allowed
+        }
+
+        Log.i(this.getClass().getName(),"Waiting for connections...");
+        while(!isCancelled()) {
+            listenSocket.setSoTimeout(1000);
+            try {
+                socket = listenSocket.accept();
+            } catch (SocketTimeoutException ignored){}
+            if (socket != null){
+                break;
+            }
+        }
+
+        Log.i(this.getClass().getName(),"Connected, " + socket.getInetAddress());
+        listenSocket.setSoTimeout(0);
+        outputStream = socket.getOutputStream();
+        inputStream = socket.getInputStream();
+    }
+
+    private void vpcdCloseClient(){
+        try {
+            outputStream.close();
+        } catch (IOException ignored) { }
+        try {
+            inputStream.close();
+        } catch (IOException ignored) { }
+        try {
+            socket.close();
+        } catch (IOException ignored) { }
+        outputStream = null;
+        inputStream = null;
+        socket = null;
+    }
+
     private void vpcdConnect(String hostname, int port) throws IOException {
+        listenSocket = null;
         socket = new Socket(InetAddress.getByName(hostname), port);
         outputStream = socket.getOutputStream();
         inputStream = socket.getInputStream();
@@ -183,5 +275,25 @@ class VPCDWorker extends AsyncTask<VPCDWorker.VPCDWorkerParams, Void, Void> {
             socket.close();
             Log.i(this.getClass().getName(), "Disconnected from VPCD");
         }
+        if  (listenSocket != null) {
+            Log.i(this.getClass().getName(), "Closing listening socket");
+            listenSocket.close();
+        }
+    }
+
+    /**
+     * Usage of API level 24+ would allow streams(), join can be removed.
+     */
+    private static String join(String separator, List<String> input) {
+        if (input == null || input.size() <= 0) return "";
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < input.size(); i++) {
+            sb.append(input.get(i));
+            if (i != input.size() - 1) {
+                sb.append(separator);
+            }
+        }
+        return sb.toString();
+
     }
 }

remote-reader/app/src/main/res/values/strings.xml

@@ -55,5 +55,6 @@
     <string name="action_delete">Clear Log</string>
 
     <string name="title_activity_settings">Settings</string>
+    <string name="hint_vpcd_listen">Listen for connections</string>
 
 </resources>

remote-reader/app/src/main/res/xml/settings.xml

@@ -32,6 +32,12 @@
             android:inputType="number"
             android:hint="Default: 35963" />
 
+        <CheckBoxPreference
+            android:key="listen"
+            android:defaultValue="false"
+            android:title="@string/hint_vpcd_listen"
+            android:hint="Default: false" />
+
     </PreferenceCategory>
 
     <PreferenceCategory