Xathrya Sabertooth

Remote Access Raspberry Pi Using Only X on Cygwin

Posted: 12 Sep 2013 10:33 AM PDT

There are some ways for accessing Raspberry Pi: access Pi directly or indirectly. You might at least try one of thus method for connecting your Pi to your PC.

The direct access involving access without any medium. You connect screen (LCD screen, for example), keyboards, mice, etc to your Pi. This way, your Raspberry Pi act as normal computer. You operate it like you operate your PC. This method has a drawback, whenever you want to use Pi you must provide appropriate input and output device (keyboard, mouse, screen).

Another way to access Pi is using indirect access. This method involving other medium to access Pi, technically a network. In this term, your Pi is connect to a network and you can access the Pi over the network. SSH and VNC are the good example of this. This method demand us to provide good network connection if you want a good connection.

Accessing Pi over network is good, you don’t need other peripheral / device such as keyboard, mouse, or LCD screen. If you want to do thing graphically you can use VNC (Virtual Network Computing). However, using VNC is somehow slow because the application and desktop environment are rendered both on your Pi and your desktop. VNC also require better network as it sends picture / screen image over time.

There is a better solution for this problem. Instead of rendering the graphic on Pi, why don’t we render it on our local computer? This way, Pi only send us minimal packet. Using this method, we can also use keyboard and mouse on our local computer, just like indirect access do.

In this article we will discuss about other way to remote accessing your desktop without VNC. If in other article we use X.org server on Linux & Unix, on this article we still use X but in cygwin environment. For this article I use:

Windows 8 on PC
cygwin64
Raspbian Wheezy on Raspberry Pi

Alternatively, you can use cygwin for 32-bit. However as my Windows 8 is 64-bit I will stick to it.

X Window System – Server & Client Architecture

X Window is originated at the Massachussetts Institute of Technology (MIT) In 1984. X11 is the system-level software infrastructure for the windowing GUI on Linux, *BSD, and other UNIX-like Operating System. It is designed to handle both local display, as well as across the network displays. X Window is a computer software system and network protocol that provides a basis for graphical user interfaces (GUIs) and rich input device capability for networked computers. It creates a hardware abstraction layer where software is written to use a generalized set of commands, allowing for device independence and reuse of programs on any computer that implements X.

X was designed from the beginning to be network-centric. It adopts a "client-server" model.

In the X model, the "X server" runs on the computer that has the keyboard, monitor, and mouse attached. The server’s responsibility includes tasks such as managing the display, handling input from the keyboard and mouse, and other input or output devices (i.e., a "tablet" can be used as an input device, and a video projector may be an alternative output device). Each X application (such as XTerm or Firefox) is a "client". A client sends messages to the server such as "Please draw a window at these coordinates", and the server sends back messages such as "The user just clicked on the OK button".

In a home or small office environment, the X server and the X clients commonly run on the same computer. However, it is perfectly possible to run the X server on a less powerful desktop computer, and run X applications (the clients) on, say, the powerful and expensive machine that serves the office. In this scenario the communication between the X client and server takes place over the network.

This confuses some people, because the X terminology is exactly backward to what they expect. They expect the "X server" to be the big powerful machine down the hall, and the "X client" to be the machine on their desk.

It is important to remember that the X server is the machine with the monitor and keyboard, and the X clients are the programs that display the windows.

Preparations

As stated before, the X window is using client/server model. Our communication would be on top of secure connection. Specifically, SSH (Secure SHell) connection are chosen to transport data (as a tunneling). Therefore, we should configure SSH server properly.

Now on your Raspberry Pi, configure SSH server. Obviously, you MUST install your SSH server program. Edit following file /etc/ssh/ssh_config, make sure these lines are not commented.

ForwardAgent yes  ForwardX11 yes  ForwardX11Trusted yes

Now open /etc/ssh/sshd_config and edit the file so it has following line:

X11Forwarding yes

Restart the SSH Server.

On our host, make sure X11 is installed on cygwin. We won’t cover how we installed cygwin or X11.

Remote Display

Open up cygwin terminal. We need an X server. At default, cygwin will not running X at startup.

We want to create a server on our local machine. This X server will manage our local screen output as well as other X client (Raspberry Pi in this case). To initiate a server, do following (assuming we use default display :0):

export DISPLAY=:0  xinit -- $DISPLAY

A new window should appear with a black blank screen. You would see a new terminal there.

Now connect to Raspberry Pi using SSH.

ssh -X user@raspberry_ip_address

user is the username we will use and the raspberry_ip_address is the Pi’s IP address. Make sure you can access and you can login to Pi.

Once you are logged in, execute this to start the X.

lxsession &  lxpanel &

Now, your window should be drawn to your Raspbian’s LXDE.

Because X on cygwin implementation is a window, you can view both your desktop and remote desktop at same time.

Proyek Teknologi

Jumat, 13 September 2013