iOS Question [Solved] Connect to JRDC2

Hello
From an Ipad I am trying to connect to JRDC2 server and I got this error :

Class not found: _dbcommand, trying: b4j.example.main$_dbcommand
(RuntimeException) java.lang.RuntimeException: Cannot serialize object: 2017-01-
31 11:50:36.0
Command: , took: 343ms, client=78.208.0.37

My client code is :

Sub Connection_Click
Log("Bouton Connection_Click pressed")
Dim xyz As DBCommand
xyz.Initialize
xyz.Name = "select_contrats"
reqManager.ExecuteQuery(xyz, 0, Null)
End Sub

from Client side I received an Error 500

Thanks for any help

Regards
Yves