Dashboards and control applications are user interfaces of system. They are displayed on end devices PC, laptops, tablets, cell phones and more and can run remotely as a web application or locally as native application. In both cases these application communicates with cloud or gateways via API (Application Interface).
API is defined as JSON messages always in the request-response form. If client needs any data simply sends request and gateway or cloud send response. Messages are sent via Websocket protocol over TCP which enables an equal initiation of communication. Either client can send data to gateway or gateway to client.
You can also go with ready to use dashboards. There are tools like Grafana, Datadog, Freeboardm Kibana and more. They have prepared components and plug-ins for many different APIs. With some level of customization effort you can get dashboard you need.
Now couple of words about where your dashboard lives. There are two options, either you have it on your device as native application (exe, Android, iPhone application) or your dashboard exist as web application and you access it via your web browser. Each solution has its pros and cons, remote deployment provides easier deployment and user accessibility.