Do not invent a custom message type. Never use unspecified values to specified stanza attributes. Use instead an extension element of you want that you message carries a special semantic.
See also
How to read custom attributes of xmpp message tag in android? - Stack Overflow
java - Adding Custom Attributes in Message tag in XMPP packet using asmack for android? - Stack Overflow
I was asking because I wanted to do some extra verfications on the server-side regarding user registration and message sending.
I’m having a hard time understanding how can I protect the Open server against a user who decompiled/deobfuscated the client application or just sniffed the network, got the server hostname/port and just spam messages or users…