changed a write on TCP/UDP/UDT to return a 'null channel', that does nothing, instead of actually return null -- so that implementing code doesn't throw a null pointer when trying to write to a socket after it has been closed. Just nothing happens now.

Dorkbox-Network/src/dorkbox/network/connection/ConnectionImpl.java

@@ -26,6 +26,7 @@ import dorkbox.network.connection.ping.PingFuture;
 import dorkbox.network.connection.ping.PingMessage;
 import dorkbox.network.connection.ping.PingUtil;
 import dorkbox.network.connection.wrapper.ChannelNetworkWrapper;
+import dorkbox.network.connection.wrapper.ChannelNull;
 import dorkbox.network.connection.wrapper.ChannelWrapper;
 
 
@@ -261,7 +262,8 @@ public class ConnectionImpl extends ChannelInboundHandlerAdapter
             if (logger2.isDebugEnabled()) {
                 logger2.debug("writing TCP while closed: {}", message);
             }
-            return null;
+            // we have to return something, otherwise dependent code will throw a null pointer exception
+            return ChannelNull.get();
         }
 
     }
@@ -283,7 +285,8 @@ public class ConnectionImpl extends ChannelInboundHandlerAdapter
             if (logger2.isDebugEnabled()) {
                 logger2.debug("writing UDP while closed: {}", message);
             }
-            return null;
+            // we have to return something, otherwise dependent code will throw a null pointer exception
+            return ChannelNull.get();
         }
     }
 
@@ -304,7 +307,8 @@ public class ConnectionImpl extends ChannelInboundHandlerAdapter
             if (logger2.isDebugEnabled()) {
                 logger2.debug("writing UDT while closed: {}", message);
             }
-            return null;
+            // we have to return something, otherwise dependent code will throw a null pointer exception
+            return ChannelNull.get();
         }
     }
 

Dorkbox-Network/src/dorkbox/network/connection/wrapper/ChannelNull.java

@@ -0,0 +1,33 @@
+package dorkbox.network.connection.wrapper;
+
+import dorkbox.network.connection.ConnectionPoint;
+
+public class ChannelNull implements ConnectionPoint {
+
+    private static final ConnectionPoint INSTANCE = new ChannelNull();
+    public static ConnectionPoint get() {
+        return INSTANCE;
+    }
+
+    private ChannelNull() {
+    }
+
+    /**
+     * Write an object to the underlying channel
+     */
+    @Override
+    public void write(Object object) {
+    }
+
+    /**
+     * Waits for the last write to complete. Useful when sending large amounts of data at once.
+     * <b>DO NOT use this in the same thread as receiving messages! It will deadlock.</b>
+     */
+    @Override
+    public void waitForWriteToComplete() {
+    }
+
+    @Override
+    public void flush() {
+    }
+}