Gateway Requirements

The gateway shall be able to poll the required points from the existing BMS or subsystems and shall have an MQTT driver.

Gateway Driver Functionality	Notes
Supported Protocols	The gateway must be able to support MQTT and whichever protocols are required to poll points from the site.
MQTT message format for publication to Senaps	JSON formatted messages are required.
MQTT message format for subscribe from Senaps	The formatting of the control signal is dependent on the DCH application, and both JSON and ASCII formatted command messages are in use. Preferably the gateway JSON driver should be able to accommodate both ASCII and JSON formatted messages.
MQTT security	Secure connection to the DCH broker via tcp_8883 is strongly recommended as this protects data and user credentials including password. For some gateways this is not supported and only unsecure messaging via tcp_1883 is supported. Some gateways require manual upload of the SSL certificate. This can be problematic as the DCH SSL certificate is updated approximately every 3 months, and if the new certificate is not manually uploaded at this time, data loss will occur.
Procedurally generated JSON messages	JSON drivers that can procedurally generate JSON messages for each point are strongly recommended. These drivers allow the user to configure strings and fields in a message template, and the JSON function block reads the specified fields from the required points and writes a JSON message for each point. Manually configured JSON messages for each point can be used, however this is recommended only for a low number of points due to workload.
Buffering
History export	The ability to export is strongly recommended where data quality is critical. DCH can accommodate history exports in JSON format where the JSON message contains point name and multiple timestamp and current value fields.