From GameBrew - a wiki dedicated to Video Game Homebrew.
A9NC - ARM9 Netload Companion
A simple companion app to receive and run ARM9 payloads via CIA & GM9 bootloader To send a firm, use: 3dslink -a [IP] [payload name] 3dslink is included in devKitARM and also available from here.
In default gm9 mode, the firm will be written to a specific location in FCRAM, where it can then be loaded from via the GodMode9 bootloader (see below).
To setup your system for gm9 mode, use GodMode9 to install the GodMode9 firm to FIRM0. GodMode9 will then act as a bootloader for typical boot.firm locations unless R+LEFT is pressed on boot.
It will also - without any required keypresses - automatically detect the firm in FCRAM and boot into it. Requires devKitARM, libctru and zlib to compile. For easy zlib installation go here.