code: private int getTangoVersionFromZmqEventSubscriptionChange() throws DevFailed {
          try {
              DeviceData  argIn = new DeviceData();
              argIn.insert(new String[] { "info" });
              DeviceData  argOut = get_adm_dev().command_inout("ZmqEventSubscriptionChange", argIn);
              DevVarLongStringArray lsa = argOut.extractLongStringArray();
              if (lsa.lvalue.length==0)
                  return -1;
              else
                  return lsa.lvalue[0];
          }
          catch (DevFailed e) {
              if (e.errors[0].reason.equals("API_CommandNotFound"))
                  return -1;
              else
                  throw e;
          }
      }
docs: ===================================================================