Handling some WebSocket connection errors gracefully (#157)

* Handling some WebSocket connection errors gracefully

* Logging only channel close events in debug mode

* Removing redundant null check

Author: hiranya911

src/main/java/com/google/firebase/database/connection/NettyWebSocketClient.java

@@ -33,6 +33,7 @@
 import io.netty.handler.ssl.SslContext;
 import io.netty.handler.ssl.SslContextBuilder;
 
+import java.io.EOFException;
 import java.net.URI;
 import java.security.KeyStore;
 import java.util.concurrent.ExecutorService;
@@ -130,8 +131,12 @@ public void close() {
 
   @Override
   public void send(String msg) {
-    checkState(channel != null && channel.isActive(), "channel not connected for sending");
-    channel.writeAndFlush(new TextWebSocketFrame(msg));
+    checkState(channel != null, "Channel not initialized");
+    if (!channel.isActive()) {
+      eventHandler.onError(new EOFException("WebSocket channel became inactive"));
+    } else {
+      channel.writeAndFlush(new TextWebSocketFrame(msg));
+    }
   }
 
   /**

src/main/java/com/google/firebase/database/connection/WebsocketConnection.java

@@ -324,8 +324,8 @@ public void run() {
 
     @Override
     public void onError(final Throwable e) {
-      if (e.getCause() != null && e.getCause() instanceof EOFException) {
-        logger.error("WebSocket reached EOF", e);
+      if (e instanceof EOFException || e.getCause() instanceof EOFException) {
+        logger.debug("WebSocket reached EOF", e);
       } else {
         logger.error("WebSocket error", e);
       }