Documentation

# DDS

The OMG Data Distribution Service (DDS™) is a middleware protocol and API standard for data-centric connectivity from the Object Management Group® (OMG®) (opens new window). It integrates the components of a system together, providing low-latency data connectivity, extreme reliability, and a scalable architecture that business and mission-critical Internet of Things (IoT) applications need.

Cyclone DDS (opens new window) is a high performing, OMG-DDS standard based data sharing technology which allows system designers to create digital twins of their systems' entities to share their states, events, data-streams and messages on the network in real-time and fault-tolerant way.

# DDS to MQTT Proxy

Here we combine dds with mqtt. So DDS node can communicate with MQTT broker.

# Building

# Iceoryx

If you have no plan to use Iceoryx, just skip this step.

$ git clone https://github.com/eclipse-iceoryx/iceoryx.git
$ cd iceoryx
$ git checkout release_2.0
$ mkdir build && cd build
$ cmake -G Ninja -DCMAKE_INSTALL_PREFIX={USER_LIBRARY_PATH} ../iceoryx_meta
$ ninja
$ sudo ninja install
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# CycloneDDS

$ git clone https://github.com/eclipse-cyclonedds/cyclonedds.git
$ cd cyclonedds
$ mkdir build && cd build
$ cmake -G Ninja -DCMAKE_INSTALL_PREFIX={USER_LIBRARY_PATH} -DCMAKE_PREFIX_PATH={USER_LIBRARY_PATH} -DBUILD_EXAMPLES=ON ..
$ ninja 
$ sudo ninja install
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Specify you installation path by USER_LIBRARY_PATH.

# DDS Proxy on NanoMQ_CLI

# Building idl-serial-code-gen

Build IDL code generator.

$ git clone https://github.com/nanomq/idl-serial.git
$ cd idl-serial
$ mkdir build && cd build
$ cmake -G Ninja -DCMAKE_INSTALL_PREFIX={USER_LIBRARY_PATH}..
$ ninja 
$ sudo ninja install
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# Build NanoMQ with DDS Proxy

  1. Specify idl file path by cmake option IDL_FILE_PATH (default path: etc/idl/dds_type.idl), enable DDS by -DBUILD_DDS_PROXY=ON ;
$ git clone https://github.com/emqx/nanomq.git 
$ cd nanomq 
$ mkdir build && cd build 
$ cmake -G Ninja -DIDL_FILE_PATH={IDL_PATH} -DCMAKE_PREFIX_PATH={USER_LIBRARY_PATH} -DBUILD_DDS_PROXY=ON .. 
$ ninja  
$ sudo ninja install
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  1. Check if dds client is built in nanomq_cli ;
$ ./nanomq_cli/nanomq_cli  
   nanomq_cli { pub | sub | conn | nngproxy | nngcat | dds } [--help] 
   
   available tools:   
     * pub   
     * sub   
     * conn   
     * nngproxy   
     * nngcat   
     * dds 
   
   Copyright 2022 EMQ Edge Computing Team
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$ ./nanomq_cli/nanomq_cli dds
 nanomq_cli dds { sub | pub | proxy } [--help] 

 available apps: 
        * sub   
        * pub   
        * proxy
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# Quick start

# Configuration

# Configuring DDS Proxy

# DDS subscription and MQTT publish

  • DDS Topic for subscribe

    • forward_rules.dds_to_mqtt.from_dds = "MQTTCMD/topic1"

  • MQTT Topic for publish

    • forward_rules.dds_to_mqtt.to_mqtt = "DDS/topic1"

  • Specify dds structure name for subscribe

    • forward_rules.dds_to_mqtt.struct_name = "remote_control_result_t"
# MQTT subscription and DDS publish

  • MQTT Topic for subscribe

    • forward_rules.dds_to_mqtt.from_dds = "DDSCMD/topic1"

  • DDS Topic for publish

    • forward_rules.dds_to_mqtt.to_mqtt = "MQTT/topic1"

  • Specify dds structure name for publish

    • forward_rules.dds_to_mqtt.struct_name = "remote_control_req_t"

Note: The struct_name must be included in the IDL file .

## Forwarding rules
forward_rules = {
	## DDS to MQTT
    dds_to_mqtt = {
        from_dds = "MQTTCMD/topic1"
        to_mqtt = "DDS/topic1"
        struct_name = "remote_control_result_t"
    }
    ## MQTT to DDS
    mqtt_to_dds = {
        from_mqtt = "DDSCMD/topic1"
        to_dds = "MQTT/topic1"
        struct_name = "remote_control_req_t"
    }
}

## DDS Configuration
dds {
    # # dds domain id
    # # default: 0
    # # Value: uint32
    domain_id = 0
    
    shared_memory = {
        # # Enable shared memory transport.
        # # Iceoryx is required if enable shared memory transport.
        # #
        # # Default: false
        # # Value:  boolean
        enable = false
        
        # # controls the output of the iceoryx runtime and can be set to, in order of decreasing output:
        # # log level: verbose, debug, info, warn, error, fatal, off
        # # Default:  info
        # # Value: enum
        log_level = info
    }
}

## MQTT client Configuration
mqtt {
	connector {
        # # Bridge address: host:port .
        # #
        # # Value: String
        # # Example: mqtt-tcp://127.0.0.1:1883
        # #          tls+mqtt-tcp://127.0.0.1:8883
        server = "mqtt-tcp://127.0.0.1:1883"
        
        # # Protocol version of the bridge.
        # #
        # # Value: Enum
        # # - 5: mqttv5
        # # - 4: mqttv311
        # # - 3: mqttv31
        proto_ver = 4
        # # The ClientId of a remote bridge.
        # # Default random string.
        # #
        # # Value: String
        # clientid="bridge_client"
        
        # # Ping: interval of a downward bridge.
        # #
        # # Value: Duration
        # # Default: 10 seconds
        keepalive = 60s
        # # The Clean start flag of a remote bridge.
        # #
        # # Value: boolean
        # # Default: false
        # #
        # # NOTE: Some IoT platforms require clean_start
        # #       must be set to 'true'
        clean_start = false
        # # The username for a remote bridge.
        # #
        # # Value: String
        username = username
        # # The password for a remote bridge.
        # #
        # # Value: String
        password = passwd
        
        ssl {
            # # enable ssl
            # # 
            # # Value: true | false
            enable = false
            # # Ssl key password
            # # String containing the user's password. Only used if the private keyfile
            # # is password-protected.
            # #
            # # Value: String
            key_password = "yourpass"
            # # Ssl keyfile
            # # Path of the file containing the client's private key.
            # #
            # # Value: File
            keyfile = "/etc/certs/key.pem"
            # # Ssl cert file
            # # Path of the file containing the client certificate.
            # #
            # # Value: File
            certfile = "/etc/certs/cert.pem"
            # # Ssl ca cert file
            # # Path of the file containing the server's root CA certificate.  
            # # 
            # # This certificate is used to identify the AWS IoT server and is publicly
            # # available.
            # #
            # # Value: File
            cacertfile = "/etc/certs/cacert.pem"
        }
    }
}
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# Running

# Iceoryx

If you don't want to start running Cyclone DDS with shared memory exchange or haven't enabled shared memory transpot layer, just skip the following steps

  1. Create an example iceoryx configuration file which has a memory pool of 2^15 blocks which can store data types of 16384 bytes (+ 64 byte header = 16448 byte block):

    [general]
version = 1

[[segment]]

[[segment.mempool]]
size = 16448
count = 32768
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    Please save this file as iox_config.toml in your own directory.

  2. Start RouDi in iceoryx in a terminal.

    $ cd {USER_LIBRARY_PATH}
$ bin/iox-roudi -c iox_config.toml
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# DDS Proxy

  1. Start MQTT Broker
$ nanomq start
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or

$ emqx start
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  1. Start DDS Proxy
$ ./nanomq_cli dds proxy --conf nanomq_dds_gateway.conf
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  1. Start MQTT client and subscribe topic DDS/topic1
$ ./nanomq_cli sub --url "mqtt-tcp://127.0.0.1:1883" -t "DDS/topic1"
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  1. Start DDS client, specify structure name remote_control_result_t and publish message ( JSON format ) to DDS topic MQTTCMD/topic1
$ ./nanomq_cli dds pub -t "MQTTCMD/topic1" --struct "remote_control_result_t"  -m '{
  "req_result_code": 1,
  "req_token": [1,2,3,4,5,6],
  "req_result_msg": [7,8,9,10,11],
  "req_id": [12,13,14],
  "req_token_len": 6,
  "req_id_len": 3
}'
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  1. Start DDS client to subscribe DDS topic MQTT/topic1 and specify structure name remote_control_req_t
$ ./nanomq_cli dds sub -t "MQTT/topic1" --struct "remote_control_req_t"
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  1. Start MQTT client to publish message ( JSON format) to MQTT topic DDSCMD/topic1
$ ./nanomq_cli pub --url "mqtt-tcp://127.0.0.1:1883" -t "DDSCMD/topic1" -m '{ 
  "req": 1,         
  "req_id": [15,16],
  "req_id_len": 2
 }'
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