Gatling support sending Array[Byte] as message with custom protocol

Hello Gatling experts.
I use gatling 2.1.5 with custom UDP extension.
I need to send message as Array[Byte] via UDP connection.
When I do so , gatling throws following exception

Simulation loadModel.ActivityManager started…
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at io.gatling.mojo.MainWithArgsInFile.runMain(MainWithArgsInFile.java:50)
at io.gatling.mojo.MainWithArgsInFile.main(MainWithArgsInFile.java:33)
Caused by: java.lang.ExceptionInInitializerError
at loadModel.ActivityManager.(ActivityManager.scala:15)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at java.lang.Class.newInstance(Class.java:379)
at io.gatling.core.runner.Runner.run(Runner.scala:36)
at io.gatling.app.Gatling$$anonfun$runSimulationIfNecessary$1.apply(Gatling.scala:132)
at io.gatling.app.Gatling$$anonfun$runSimulationIfNecessary$1.apply(Gatling.scala:117)
at scala.Option.getOrElse(Option.scala:121)
at io.gatling.app.Gatling.runSimulationIfNecessary(Gatling.scala:117)
at io.gatling.app.Gatling.start(Gatling.scala:73)
at io.gatling.app.Gatling$.fromArgs(Gatling.scala:59)
at io.gatling.app.Gatling$.main(Gatling.scala:44)
at io.gatling.app.Gatling.main(Gatling.scala)
… 6 more
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to [B
at loadModel.Calamp3030And5000MessageType2$.(Calamp3030And5000MessageType2.scala:52)
at loadModel.Calamp3030And5000MessageType2$.(Calamp3030And5000MessageType2.scala)
… 21 more

(sending message as String works good for gatling ,but sends wrong data to the endpoint)

Is it possible ,gatling handles only String messages ?

Can someone please direct me how to solve this problem?
Why Gatling cares, what kind of data has been sent?

Any help will be appreciated.