AirLogger - A simple remote console log viewer for node.js (server) and iOS (client) by @c0diq

MOTIVATION

At MOG, I needed a way to debug iOS apps while connected to a USB accessory or video out display. In this situation, it's not possible to debug an app or accessing the device console. The only choice is to disconnect the device from the accessory and connect it back to the computer to analyze the console log which is very time consuming.

The idea here is to have a background app (AirLogger) that fetches console log entries and send them in real time over WiFi to another machine while the device stays connected to the accessory with the monitored app running in the foreground.

OVERVIEW

The system consists of 2 components:

• A Server to receive log entries from clients. I chose a leverage a simple and robust pubsub fanout messaging server for node.js written by @jazzychad https://github.com/c0diq/fanout.node.js

Since I didn't want to have to enter the IP address of the server in the client, I've also added Bonjour announcement using node_mdns for node.js by @agnat https://github.com/agnat/node_mdns

• A Client iOS app that runs in the background and uses ASL C functions to access the iOS console log entries. Interestingly these are public APIs. As you know, a vanilla iOS app can run in the background in iOS4 and above for only up to 10 minutes. For more time, a trick used here is to pretend to need background audio and play silence. DISCLAIMER: This will not be approved by Apple. Don't try to submit your app with this trick.

[The original fanout server separated clients (subscribers) from controllers (publishers). This version doesn't differentiate the two different types. All clients can publish and subscribe in the airlogger model. This allows a client to not only send logs but in the future, receives commands as well.]

SETUP

The airlogger fanout pubsub system consists of three parts o The "airlogger server" itself o One or more "Clients" (message subscribers/publishers)

The airlogger server is run as a node.js process. Clients connect to the server on the client port (default 1986).

Clients can do 5 (five) things: o Subscribe to message channels o Unsubscribe from message channels o Receive messages on subscribed message channels o Ping the fanout server for the current unix millitime o Send (publish) messages on message channels

Upon connection, each Client is automatically subscribed to the "all" message channel, so that if another Client publishes a message to the "all" message channel, each Client will receive it. This is useful for sending system-wide messages to all connected clients. Clients can choose to unsubscribe from the "all" channel if they so choose. Also upon connection, each client will receive a message on the "debug" message channel notifying them that they have connected to the server.

USAGE

Assuming you have installed node.js on your machine/server, all you need is this:

node Server/airlogger.js

Alternatively, you can install airlogger using npm:

npm install airlogger

NOTE: Using npm will take care of installing all the dependencies (fanout, mdns, winston)

To start sending log entries, open the AirLogger.xcodeproj in XCode and deploy to your iOS device The App starts looking for _airlogger._tcp mdns services on the network.

If your iOS device and airlogger server machine are on the same network, the server should appear in the list of available servers. All console log entries will immediately be sent to the selected server.

You can then background the AirLogger app and launch the app you want to monitor.

Log entries are sent by the iOS client using the following format: