Hi! We are the developers of Mongoose, the most popular embedded networking library.
Recently, we have ported it to nRF51 / nRF52 - see step-by-step demo at: https://www.hackster.io/dfrank/mongoose-embedded-networking-library-on-nrf52-547b15
Now, the rich set of networking API - like HTTP/WebSocket/MQTT/mDNS/CoAP, is available on Nordic chips. Official SDK lacks support for some widely used protocols like HTTP and WebSocket, and Mongoose provides it!
What Mongoose can do? Turn a device into a RESTful server - make it controllable via a browser! Or, call an external RESTful server. Or, create a Web UI for a device. Push data in real-time over WebSocket or MQTT. Or, make a device discoverable in the local network (mDNS/dns-SD, Bonjour). Or, .. many more other possibilities!
See a long list of ready-made examples at https://github.com/cesanta/mongoose/tree/master/examples