Implementing an MQTT Client

次のレポートYMQTT_CLIENT_TESTは、MQTTクライアントの簡単な実装を提供します。MQTTクライアントの簡単な例として、公開されているMQTTブローカーをターゲットサーバーとして使用できます。この例では、WebSocketベースのHiveMQブローカーws：//broker.hivemq.com：8000/mqttを使用しています。ローカルインストールとしてMosquittoなど、MQTTプロトコルのバージョン3.1.1をサポートする任意のMQTTブローカーを使用することもできます。
サンプルコード
*&---------------------------------------------------------------------**& Report YMQTT_CLIENT_TEST*&---------------------------------------------------------------------**&*&---------------------------------------------------------------------*REPORT ymqtt_Client_test.CLASS lcl_mqtt_event_handler DEFINITION CREATE PUBLIC FINAL.  PUBLIC SECTION.    INTERFACES: if_mqtt_event_handler.     " for the on_* handling    DATA: mv_on_subscribe_message_nr   TYPE int8.    DATA: mv_on_publish_message_nr     TYPE int8.    DATA: mv_on_unsubscribe_message_nr TYPE int8.    DATA: mv_on_message_message_nr     TYPE int8.    DATA: mo_message                    TYPE REF TO if_mqtt_message,          mv_message_topic              TYPE string.ENDCLASS.CLASS lcl_mqtt_event_handler IMPLEMENTATION.  METHOD if_mqtt_event_handler~on_connect.     " connect handling  ENDMETHOD.  METHOD if_mqtt_event_handler~on_message.    TRY.        me->mv_message_topic = i_topic_name.        me->mo_message       = i_message.        me->mv_on_message_message_nr    = i_envelope->get_message_number( ).      CATCH cx_mqtt_error INTO DATA(lx_mqtt_error).        " error handling    ENDTRY.  ENDMETHOD.  METHOD if_mqtt_event_handler~on_publish.    TRY.        me->mv_on_publish_message_nr = i_envelope->get_message_number( ).      CATCH cx_mqtt_error INTO DATA(lx_mqtt_error).        " error handling     ENDTRY.  ENDMETHOD.  METHOD if_mqtt_event_handler~on_subscribe.    TRY.        me->mv_on_subscribe_message_nr = i_envelope->get_message_number( ).      CATCH cx_mqtt_error INTO DATA(lx_mqtt_error).             " error handling    ENDTRY.  ENDMETHOD.  METHOD if_mqtt_event_handler~on_unsubscribe.    TRY.        me->mv_On_unsubscribe_message_nr = i_envelope->get_message_number( ).      CATCH cx_mqtt_error INTO DATA(lx_mqtt_error).        " error handling     ENDTRY.  ENDMETHOD.  METHOD if_mqtt_event_handler~on_disconnect.    " disconnect handling  ENDMETHOD.ENDCLASS.START-OF-SELECTION.  TRY.      DATA(lo_mqtt_event_handler) = NEW lcl_mqtt_event_handler( ).      " create MQTT client      cl_mqtt_client_manager=>create_by_url(        EXPORTING          i_url            = 'ws://broker.hivemq.com:8000/mqtt'          i_event_handler  = lo_mqtt_event_handler        " i_proxy            = … " optional setting of proxy host/port        " i_ssl_id           = … " optional setting of SSL certificate ID        RECEIVING          r_client        = DATA(lo_mqtt_client) ).      " establish the connection      lo_mqtt_client->connect( ).      " subscribe to topic filter with QoS      DATA(lt_mqtt_topic_filter_qos) =            VALUE if_mqtt_types=>tt_mqtt_topic_filter_qos(                         ( topic_filter = 'abaptopic/#'                           qos          = if_mqtt_types=>qos-at_most_once ) ).      CLEAR: lo_mqtt_event_handler->mv_on_subscribe_message_nr.      lo_mqtt_client->subscribe(          EXPORTING             i_topic_filter_qos = lt_mqtt_topic_filter_qos          IMPORTING             e_envelope         = DATA(lo_envelope_subscribe) ).      WRITE: /'Subscribe topic filter:     ',                lt_mqtt_topic_filter_qos[ 1 ]-topic_filter,             /'Subscribe QoS:              ',                lt_mqtt_topic_filter_qos[ 1 ]-qos,             /'Subscribe message number:   ',                lo_envelope_subscribe->get_message_number( ).            " wait for acknowledgement, i.e. execution of on_subscribe      WRITE: /.      WRITE: /'WAIT FOR PUSH CHANNELS ...'.      WRITE: /.      WAIT FOR PUSH CHANNELS UNTIL                     lo_mqtt_event_handler->mv_on_subscribe_message_nr > 0                     UP TO 10 SECONDS.      IF lo_mqtt_event_handler->mv_on_subscribe_message_nr = 0.        MESSAGE 'On_Subscribe is not executed !' TYPE 'E'.      ELSE.        WRITE: /'On_Subscribe message number:',                  lo_mqtt_event_handler->mv_on_subscribe_message_nr.      ENDIF.      " publish message to topic name and QoS      DATA(lo_mqtt_message) = cl_mqtt_message=>create( ).      lo_mqtt_message->set_qos( if_mqtt_types=>qos-at_most_once ).      lo_mqtt_message->set_text( 'Hello MQTT World ;-)'  ).      CLEAR: lo_mqtt_event_handler->mv_on_publish_message_nr,              lo_mqtt_event_handler->mo_message.             lo_mqtt_client->publish(                         EXPORTING i_topic_name = 'abaptopic/test'                                  i_message    = lo_mqtt_message                        IMPORTING e_envelope   = DATA(lo_envelope_publish) ).      WRITE: /.      WRITE: /'Publish topic name:         ',              lo_envelope_publish->get_topic_name( ),             /'Publish QoS:                ',              lo_envelope_publish->get_message( )->get_qos( ),             /'Publish message text:       ',              lo_envelope_publish->get_message( )->get_text( ),             /'Publish message number:     ',              lo_envelope_publish->get_message_number( ).      " wait for receiving ("echo-ing back") of published message       WRITE: /.      WRITE: /'WAIT FOR PUSH CHANNELS ...'.      WRITE: /.      WAIT FOR PUSH CHANNELS UNTIL                     lo_mqtt_event_handler->mv_on_publish_message_nr > 0 AND                     lo_mqtt_event_handler->mo_message IS NOT INITIAL                     UP TO 10 SECONDS.      IF lo_mqtt_event_handler->mo_message IS INITIAL.        MESSAGE 'Message is not received!' TYPE 'E'.      ELSE.        WRITE: /'On_Publish message number:',                lo_mqtt_event_handler->mv_on_publish_message_nr.                WRITE: /.        WRITE: /'On_Message topic name:    ',                lo_mqtt_event_handler->mv_message_topic,                               /'On_Message QoS:           ',                lo_mqtt_event_handler->mo_message->get_qos( ),               /'On_Message message text:  ',                lo_mqtt_event_handler->mo_message->get_text( ).      ENDIF.      " unsubscribe the topic filter      DATA(lt_mqtt_topic_filter) = VALUE if_mqtt_types=>tt_mqtt_topic_filter(                                          ( topic_filter = 'abaptopic/#' ) ).       lo_mqtt_client->unsubscribe(                   EXPORTING i_topic_filter = lt_mqtt_topic_filter                  IMPORTING e_envelope     = DATA(lo_envelope_unsubscribe) ).      " disconnect the connection      lo_mqtt_client->disconnect( ).    CATCH cx_apc_error INTO DATA(lx_apc_error).      " error handling      MESSAGE lx_apc_error->get_text( ) TYPE 'E'.    CATCH cx_mqtt_error INTO DATA(lx_mqtt_error).      " error handling      MESSAGE lx_mqtt_error->get_text( ) TYPE 'E'.  ENDTRY.