AppleConnect – Streamlining Local Network With Bonjour

AppleConnect is a small Swift wrapper around a Network TCP stream on the local network (using Bonjour for discovery).

Even though the transport is two-way, the API is built around a “service” that is offered by a single server and to which many clients can connect.

Usage

Setup for servers differs a little bit from that for clients. Once a connection is established, the channel is identical from both ends. All connections are encrypted using TLS-PSK derived from a shared key of your choosing.

Important

For security, you should generate the shared key using cryptographically appropriate random data. Sharing this key should be done out-of-band and is out of scope for AppleConnect.

For user-facing applications, one way you might do this is by generating a code on one device and asking the user to confirm it on the second one.

Setting Up The Server

A typical server should advertise its availability using Connection.advertise(forServiceType:name:key:). Attempts by clients to connect will show up as NWConnection objects, which you can pass to Connection.init(connection:) to complete the connection process.

Setting Up The Client

A client should browse for servers it wants to connect to. Connection.endpoints(forServiceType:) will asynchronously stream a list of available NWEndpoints, and once you’ve found an endpoint that you’d like to connect to, call Connection.init(endpoint:key:) to establish the connection using the shared encryption key.

Transferring Data

Both clients and servers can send data to each other using Connection.send(data:), and receive data by watching Connection.data.