How to set a sender proxy message to EOIO (serialization). Call this serialize() method just prior to execute().

proxy_serialize.abap

method serialize.
  "importing io_proxy  type ref to cl_proxy_basis  
  "raising cx_ai_system_fault  

  data:
    lo_async_messaging  type ref to if_wsprotocol_async_messaging.

  queue = get_queue_name( ).

  check not queue is initial.

  try.
      lo_async_messaging ?= io_proxy->get_protocol( if_wsprotocol=>async_messaging ).
      check lo_async_messaging is bound.
      lo_async_messaging->set_serialization_context( queue ).
    catch cx_sy_move_cast_error.
  endtry.

endmethod.