In this article I will show you how to take control of a remote Linux desktop with the help of x11vnc, Remote Desktop Viewer, and secure shell. You will, of course, have to have secure shell access to the remote machine. Other than that you have everything you need. So let’s get to work.

Installation

You will need the following installed in order to take on this task.

Local machine

• VNC client (such as gtk vnc)
• Ssh client (openssh works fine)

Remote machine

• Ssh server (openssh-server works great)
• VNC server (x11vnc is my recommdation)

Fire up your package management tool, search for the above applications, and install each. If you do not already have the secure shell server installed on the remote machine, you will need physical access in order to install the tools. If you already have the ssh server installed you can simply ssh to the remote machine and install the VNC server from command line (such as sudo apt-get install x11vnc) Once you have these installed you are ready to start setting up your connection.

x11vnc

The first thing you need to do is secure shell to the remote machine (we’ll say the remote machine is at IP address 192.168.1.10) and start up the VNC server. From the command line (on the remote machine) you will enter the command x11vnc. This will start the VNC server but you will not get your bash prompt returned to you. To have your VNC server running at all times you could add the line:

x11vnc &

to the end of your /etc/rc.local

The Client Machine

Figure 1

For the purposes of this tutorial I will use the Gtk VNC Viewer. It is a very simple to use, up to date, client. You will find this tool in Applications > Internet. When you first start it up you will see a fairly straight-forward connection window. You only need enter:

• IP Address:Port: IP address and port of the remote machine (in the form of 192.168.1.10:5900). NOTE: x11vnc uses port 5900 by default.
• User name: The user name you will connect with on the remote machine.
• Password: Password of the user on the remote machine.

If you know the above information is correct (and you know you’ll be connecting to this machine again) click the Add button to add the remote machine (as shown in Figure 1).

To connect to the remote machine either enter the information in the text areas and click the Connect button or double click on a saved machine from the list.

Figure 2

When you connect a new, maximized window will open showing your remote desktop (see Figure 2). From this window you can do the following:

• Disconnect: Disconnect from the remote machine.
• Send keys: Send key-combinations to the remote machine.
• Fullscreen: Switch to a full screen window.
• Screenshot: Take a screen shot of the remote desktop.
• Make icon on desktop: Create an icon that allows you to connect to this remote desktop with a double-click.

You can now interact with this remote machine as if it were your own desktop.

Final thoughts

Taking advantage of the remote desktop is a great way to train users or trouble shoot problems on a remote machine. I use this exact setup for a number of clients. It works well.

AutoPutty is a portable software program for Windows that can manage servers for all four software clients that have been mentioned in this article. Manage in this regard means that system administrators and webmasters can add server information, that is hostname or IP, port, username, password and type (WinSCP SCP or SFTP, Putty, Remote Desktop or VNC) in the program to connect to the server more quickly.

The system administrator can access the options of Autoputty to define the paths to the various applications and other settings like commands that should be executed or private key files for authentication (where supported). It is furthermore possible to password protect the application itself so that only authorized users are able to manage the connections and servers.

Autoputty (via Techie Buzz) is a free download for the Windows operating system. It requires the Microsoft .net Framework 2.0 and uses less than one Megabyte of computer memory in minimized state. The biggest benefit of the program for system administrators is that it can manage servers for several applications which makes it a tad easier to maintain and connect to them.

VNC is a very popular remote desktop software that can be used to view a remote system’s desktop. It’s main limitation is that it can only be used to view one system at a time. VNC Thumbnail Viewer has been created to overcome this limitation. It is a remote desktop software that will display a realtime thumbnail image of remote computers on a server system. The software program comes with two components: A server program that has to be installed on all remote computer systems as this program sends screenshots of the desktop over the network. The viewer component can be run to display the desktops of the remote computer systems that send the desktop screenshots over the network.

The installation of VNC Thumbnail Viewer is outlined below:

• Start VNC Server on all remote computer systems. You also need to ensure that a VNC client like UltraVNC or TightVNC.
• Start VNC Thumbnail Viewer on another computer system.
• Connect it to the remote computer systems by entering their IP or Hostname, port number and server password. The window will automatically scale depending on the number of connected vnc servers
• A double-click will will open that server in a new window giving the admin control of the keyboard and mouse

The VNC Thumbnail Viewer application is available for Windows, Linux and OS X.

I am not a big tutorial-fan, cause I always can’t quite shake the feeling that I’m doing something here I have no particular knowledge of. And depending on what I do, this bothers me. A lot. Take sewing for instance (yes, I do indeed enjoy the fun of sewing, at least as long as it is fun); in the beginning I only did pre-set tutorials. I got to see some achievements, pretty fast as well, and was happy. But the clothings didn’t fit that well, more often than not I had to make corrections to be at least a bit satisfied with my work.

By now, I do most of my sewing patterns myself by taking bits from tutorials and knowledge and putting them together, and it works just fine for me. My point is, tutorials are often brief, giving appealing results in a short time, but often lack some of the necessary theory. Ever happened to you that you did something with a tutorial that just would not work? And after going through the complete text again, looking at all pictures, you realize there’s a small mistake in it, or something you wouldn’t have thought of, which the author took as given?

I guess that’s the reason I don’t want to write tutorials, the danger of missing something (or to cut off too much or something like that) or to have people sitting in front of it thinking “Screw this guy, this just doesn’t work!”. Plus, there are plenty of tutorials out there regarding nearly any topic. Or are there?

But – as the headline suspects – I’m gonna break with this habit for now, and give you a few shots and explanations regarding my former post. No tutorial in a classical sense, but one like I try to write my stuff as well: just concepts and ideas, but this time with pictures.

So let’s get started. Since I’m keeping my connection open most of the time, I’m using PuTTyTray instead of the regular PuTTy or its portable cousin, so some functions described here are not available in other versions.

Here we got the starting screen. Use “Settings from file” (at the bottom of the screen) to save sessions to a file in the PuTTy-directory instead of the windows-registry. An absolute must for all portable users. The first ellipse is where you type your target server’s (or router’s, in our case) IP in. If you can’t remember your IP at any time or get dynamic IPs, make an dyndns-account to save you trouble. Most Routers come with built-in dyndns-support anyway nowadays, sparing you the effort of an update tool. Of course, we want to have “SSH” as a connection type, but it’s per default enabled, so there shouldn’t be any problems.

Ah, that one took me awhile to figure out. Or to be more precise: I was swearing and cursing about the problem I encountered and by accident managed to find a solution in the settings for my terminal, which struck me to be very odd. So I wanna share my insights. The option I circled changes the character send to the server by pressing the backspace-key. Since the routers I mentioned all use some sort of linux, you might wanna change the option to the right one, “Control+? (127)”. Without that enabled, my fritzbox would only type “[^” or something like that instead of deleting the last character. Very annoying.

That one is one of the PuTTyTray-only functions I mentioned that I don’t wanna miss ever again, regardless how more convenient PuTTyPortable sometimes might be for my purposes. Leave the option on “normal” to start it in normal terminal mode. I prefer that one, since I want to use password-authentication. No use minimizing the window to tray on start, only to have to bring it back up, type the password in and minimize it again. “Always” and “Never” produced funny behaviors that I couldn’t get a hold of, but, if you wanna guess and like riddles, go and give it a try.

And oh, the “Accept single-click…”-option is nice as well, if you use this kind of restoring in all of your programs. Mixing double-click and single-click is definitely not a good idea, at least not for me.

Oh, yeah. Not that important, I gotta admit. But it would allow you to pick a username that’s hard to remember (please don’t say anything about the “root” I typed in there.. it is for demonstration purposes only!), and even harder to guess. When using password authentication, I only have to type in my password and not my username. spares me ~1.2 seconds. yay!

Painting Frenzy!! Okay, now here we go. This tab is the mekka for all your needs, the holy grail of port forwarding.
The first option I circled is recommended to use, but it is not without risks (security, mostly). Some protocols may need this option to function properly though. When you look at the entries 1, 2 and 3 they all have a source port (the first column) and a destination (the second one), like my arrows – done extremely skilled, if I may say so – try to show you.

1.) This is a standard port forwarding like used by any program. I specified my source port, which is 5700 (always select “local” as a type if unsure for the others and their doings), and a destination that is usually an IP plus a port. As you can see or at least guess, it’s for VNC (port 5900), and it’s for a fictional desktop in my home network.

2.) That one I use for the emulation of a vpn. Remember the virtual network adapter I had to create? I gave it the very innovative IP 10.0.0.1, Windows File Sharing services use port 139, so its 10.0.0.1:139 for source. The destination is my main network-hard drive with the very same port. If you specify an IP for the source port, the port is only forwarded if the accordant network adapter is used. In case of the file sharing, I had to do this, since I wanted to work both ways at the same time – local file sharing and file sharing over SSH. If you need only one of both, feel free to just forward the port without a source IP.

3.) This one is pretty much like the first, but it points to a virtual network card I created on my Router. I did so because it is forbidden to map any ports directly to the routers own IP, but mapping to the virtual NIC is allowed. Here, I’m forwarding localhost’s port 80 (do NOT do this when running a webserver or any software using port 80) to the virtual NIC’s port 80, so I can display my router’s status page in my browser here at work, taking a look at phone lists and the like. I also could’ve made a port forwarding like “6666 192.168.178.253:80″, to view my routers page then, I would have to connect to “localhost:6666″ in my browser, as well as for connecting my VNC, I have to connect to “<dyndns-address>:5700″ instead of just “<dyndns-address>”.

Be careful with the Connection -> Proxy-Tab though. You don’t have to specify anything here for PuTTy to provide the SOCKS-proxy I mentioned. This is only necessary if PuTTy is forced (or wanted) to use a proxy to connect to the target net (usually, the internet) itself, like when using PuTTy over TOR for instance, which is by the way in my opinion the most comfortable way of using TOR there is.

Oh my, I almost forgot that one.. this is crucial when keeping your connection up and running for a long time. If the connection gets broken there is a chance that your server-component remains active and running on the router, and if your reconnect, you got a second one running, and a third one if that happens again.. you catch my drift. I chose a value of 60 seconds, and it works for me. It was a more or less random choice though, other values might do equally fine.

Okay. I admit, that didn’t hurt that much at all. Maybe I will just… keep posting funny daubed pictures about programs I use…

cya all soon! :)

All that needs to be done is download the CrossLoop application and run it at both computers that shall take part in the process. The host, that is the computer that sends it screens to the other computer, has to setup an access code and the computer that wants to join has to enter that access code to be able to establish the connection. A random access code is generated when you click on the Host tab.

This works well even if the computers are secured with a firewall or other means of protection and requires no configuration of them. Routers do not have to be configured as well, just run and connect.

Requirements are that both computers run Windows 98 or later and have at least 128 MB of Ram and 2 MB of hard drive space.

Found this great tool at the donation coder blog.