Added timer based reverse connection blacklist to avoid infinite loop when two Android 5.0 devices are trying to connect

Changed netty all to netty handler, netty handler is smaller in size and contains required components

src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java

@@ -21,6 +21,7 @@
 package org.kde.kdeconnect.Backends.LanBackend;
 
 import android.content.Context;
+import android.os.Build;
 import android.preference.PreferenceManager;
 import android.support.v4.util.LongSparseArray;
 import android.util.Base64;
@@ -39,8 +40,13 @@ import java.net.InetSocketAddress;
 import java.security.cert.Certificate;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.Set;
+import java.util.Timer;
+import java.util.TimerTask;
+import java.util.concurrent.TimeUnit;
 
 import javax.net.ssl.SSLEngine;
+import javax.net.ssl.SSLHandshakeException;
 
 import io.netty.bootstrap.Bootstrap;
 import io.netty.bootstrap.ServerBootstrap;
@@ -67,7 +73,6 @@ import io.netty.handler.codec.string.StringEncoder;
 import io.netty.handler.logging.LogLevel;
 import io.netty.handler.logging.LoggingHandler;
 import io.netty.handler.ssl.SslHandler;
-import io.netty.util.AttributeKey;
 import io.netty.util.CharsetUtil;
 import io.netty.util.concurrent.Future;
 import io.netty.util.concurrent.GenericFutureListener;
@@ -86,6 +91,9 @@ public class LanLinkProvider extends BaseLinkProvider {
     private TcpHandler tcpHandler = new TcpHandler();
     private UdpHandler udpHandler = new UdpHandler();
 
+    private ArrayList<String> reverseConnectionBlacklist = new ArrayList<>();
+    private Timer reverseConnectionTimer;
+
     @ChannelHandler.Sharable
     private class TcpHandler extends SimpleChannelInboundHandler<String>{
         @Override
@@ -252,6 +260,23 @@ public class LanLinkProvider extends BaseLinkProvider {
 
                             if (!future.isSuccess()) {
                                 Log.e("KDE/LanLinkProvider", "Cannot connect to " + identityPackage.getString("deviceId"));
+                                // Try reverse connection
+
+                                if (!reverseConnectionBlacklist.contains(identityPackage.getString("deviceId"))) {
+                                    // We are waiting for 3 seconds after trying reverse connection, to avoid any further emmission
+                                    // Without this, infinite loop is created between two devices with Android 5.0, because server will not work on it
+                                    // and it will cause trouble for ohter devices too
+                                    reverseConnectionTimer = new Timer();
+                                    reverseConnectionTimer.schedule(new TimerTask() {
+                                        @Override
+                                        public void run() {
+                                            reverseConnectionBlacklist.remove(identityPackage.getString("deviceId"));
+                                        }
+                                    }, 3*1000);
+                                    reverseConnectionBlacklist.add(identityPackage.getString("deviceId"));
+                                    onNetworkChange();
+                                }
+
                                 return;
                             }
 
@@ -378,21 +403,6 @@ public class LanLinkProvider extends BaseLinkProvider {
 
         this.context = context;
 
-        bossGroup = new NioEventLoopGroup(1);
-        workerGroup = new NioEventLoopGroup();
-        try{
-            ServerBootstrap tcpBootstrap = new ServerBootstrap();
-            tcpBootstrap.group(bossGroup, workerGroup);
-            tcpBootstrap.channel(NioServerSocketChannel.class);
-            tcpBootstrap.option(ChannelOption.SO_BACKLOG, 100);
-            tcpBootstrap.handler(new LoggingHandler(LogLevel.INFO));
-            tcpBootstrap.option(ChannelOption.SO_REUSEADDR, true);
-            tcpBootstrap.childHandler(new TcpInitializer());
-            tcpBootstrap.bind(new InetSocketAddress(port)).sync();
-        }catch (Exception e) {
-            e.printStackTrace();
-        }
-
         udpGroup = new NioEventLoopGroup();
         try {
             Bootstrap udpBootstrap = new Bootstrap();
@@ -416,6 +426,26 @@ public class LanLinkProvider extends BaseLinkProvider {
 
         clientGroup = new NioEventLoopGroup();
 
+        if (Build.VERSION.SDK_INT == Build.VERSION_CODES.LOLLIPOP) {
+            // Server not working in Android Lollipop due to ssl bug
+            return ;
+        }
+
+        bossGroup = new NioEventLoopGroup(1);
+        workerGroup = new NioEventLoopGroup();
+        try{
+            ServerBootstrap tcpBootstrap = new ServerBootstrap();
+            tcpBootstrap.group(bossGroup, workerGroup);
+            tcpBootstrap.channel(NioServerSocketChannel.class);
+            tcpBootstrap.option(ChannelOption.SO_BACKLOG, 100);
+            tcpBootstrap.handler(new LoggingHandler(LogLevel.INFO));
+            tcpBootstrap.option(ChannelOption.SO_REUSEADDR, true);
+            tcpBootstrap.childHandler(new TcpInitializer());
+            tcpBootstrap.bind(new InetSocketAddress(port)).sync();
+        }catch (Exception e) {
+            e.printStackTrace();
+        }
+
     }
 
     @Override