GCtrl

Downloading
Processing Script to stream Gcode

You'll also need to download Processing. Processing is an open source programming language and environment Download and unzip from the Processing.org site. Be sure to select the correct version for your OS.

Installation and configuration
Serial port choosing not working correctly, it's better to edit code and select the port there. Quite simple process, just have to comment one line, uncomment another and edit that.
 * Open Processing and open the downloaded .PDE file.
 * Find out which number is your serial port.
 * For Linux it should be like ttyUSBx or ttyACMx where x is a number. Use this command to find out. ls /etc/tty*
 * For Windows:
 * Windows XP: Right click on "My Computer", select "properties", select "device manager".
 * Windows 7: Start -> Right Click Computer -> Select Manage -> Select Device Manager from left pane
 * In the tree, expand "Ports (COM & LPT)"
 * Your arduino will be the USB Serial Port (COMX), where the “X” represents the COM number.
 * For Mac
 * To find the device path, from a Terminal.app window, type: /dev/tty.usb and hit Tab once or twice. This will give you the device name and path.
 * Comment the line String portname = null;
 * Uncomment the line corresponding to your system and edit it to reflect your serial port info.