Discard unsupported messages instead of disconnecting the peer.

src/main/java/org/qortal/network/Peer.java

@@ -12,6 +12,7 @@ import org.qortal.data.network.PeerData;
 import org.qortal.network.message.ChallengeMessage;
 import org.qortal.network.message.Message;
 import org.qortal.network.message.MessageException;
+import org.qortal.network.message.UnsupportedMessageException;
 import org.qortal.network.task.MessageTask;
 import org.qortal.network.task.PingTask;
 import org.qortal.settings.Settings;
@@ -510,8 +511,13 @@ public class Peer {
                     ByteBuffer readOnlyBuffer = this.byteBuffer.asReadOnlyBuffer().flip();
                     try {
                         message = Message.fromByteBuffer(readOnlyBuffer);
+                    } catch (UnsupportedMessageException e) {
+                        // Unsupported message - discard it without disconnecting
+                        LOGGER.debug("[{}] {}, from peer {} - discarding...", this.peerConnectionId, e.getMessage(), this);
+                        return;
                     } catch (MessageException e) {
-                        LOGGER.debug("[{}] {}, from peer {}", this.peerConnectionId, e.getMessage(), this);
+                        // Any other message exception - disconnect the peer
+                        LOGGER.debug("[{}] {}, from peer {} - forcing disconnection...", this.peerConnectionId, e.getMessage(), this);
                         this.disconnect(e.getMessage());
                         return;
                     }

src/main/java/org/qortal/network/message/Message.java

@@ -104,7 +104,7 @@ public abstract class Message {
 			MessageType messageType = MessageType.valueOf(typeValue);
 			if (messageType == null)
 				// Unrecognised message type
-				throw new MessageException(String.format("Received unknown message type [%d]", typeValue));
+				throw new UnsupportedMessageException(String.format("Received unknown message type [%d]", typeValue));
 
 			// Optional message ID
 			byte hasId = readOnlyBuffer.get();

src/main/java/org/qortal/network/message/UnsupportedMessageException.java

@@ -0,0 +1,19 @@
+package org.qortal.network.message;
+
+@SuppressWarnings("serial")
+public class UnsupportedMessageException extends MessageException {
+    public UnsupportedMessageException() {
+    }
+
+    public UnsupportedMessageException(String message) {
+        super(message);
+    }
+
+    public UnsupportedMessageException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public UnsupportedMessageException(Throwable cause) {
+        super(cause);
+    }
+}