diff --git a/pom.xml b/pom.xml
index 06bbb9c..e5e2093 100644
--- a/pom.xml
+++ b/pom.xml
@@ -13,8 +13,8 @@
     <jdk.version>11</jdk.version>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <project.build.targetEncoding>UTF-8</project.build.targetEncoding>
-    <maven.compiler.source>11</maven.compiler.source>
-    <maven.compiler.target>11</maven.compiler.target>
+    <!-- <maven.compiler.source>11</maven.compiler.source>
+    <maven.compiler.target>11</maven.compiler.target> -->
   </properties>
 
 
@@ -48,6 +48,15 @@
   <build>
     <plugins>
       <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.8.1</version>
+        <configuration>
+          <release>11</release> 
+        </configuration>
+      </plugin>
+
+      <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>exec-maven-plugin</artifactId>
         <version>3.0.0</version>
diff --git a/src/main/java/info/istlab/ServerTester/JTAConsole.java b/src/main/java/info/istlab/ServerTester/JTAConsole.java
index d1beefc..eaf2e05 100644
--- a/src/main/java/info/istlab/ServerTester/JTAConsole.java
+++ b/src/main/java/info/istlab/ServerTester/JTAConsole.java
@@ -156,6 +156,7 @@
 
     @Override
     public void windowClosing(WindowEvent e) {
+        requestFocus();
         destroyProcess();
 
         winStack.remove(this);
diff --git a/src/main/java/info/istlab/ServerTester/MulticastReceiver.java b/src/main/java/info/istlab/ServerTester/MulticastReceiver.java
index d922a70..175ac26 100644
--- a/src/main/java/info/istlab/ServerTester/MulticastReceiver.java
+++ b/src/main/java/info/istlab/ServerTester/MulticastReceiver.java
@@ -5,6 +5,7 @@
 import java.net.InetSocketAddress;
 import java.net.StandardProtocolFamily;
 import java.nio.ByteBuffer;
+import java.nio.channels.AsynchronousCloseException;
 import java.nio.channels.DatagramChannel;
 import java.util.Hashtable;
 
@@ -47,6 +48,9 @@
             InetSocketAddress senderAddr = null;
             try {
                 senderAddr = (InetSocketAddress) channel.receive(buffer);
+            } catch(AsynchronousCloseException ace){
+                thread = null;
+                break;
             } catch (IOException e) {
                 e.printStackTrace();
             }
@@ -55,6 +59,10 @@
             byte[] data = new byte[buffer.remaining()];
             buffer.get(data);
             String message = new String(data);
+            if (senderAddr == null) {
+                thread = null;
+                break;
+            }
             String addr = senderAddr.getAddress().getHostAddress();
             receivedData.put(addr, message);