better network structure

app/src/main/java/network/protocol/Packet.java

@@ -0,0 +1,11 @@
+package network.protocol;
+
+import java.io.Serializable;
+
+public abstract class Packet implements Serializable {
+
+	// public abstract int getId();
+
+	public abstract void accept(PacketVisitor packetVisitor);
+
+}