Posts Tagged ‘Linux’

Greetings from GNOME

December 27, 2009 Leave a comment

Now this is really useful: there is a GNOME panel applet for writing blog posts (for the Debian/Ubuntu folks: it’s in the package gnome-blog). Just gotta try it out 🙂

Edit: Unfortunately, there is no possibility to assign tags or categories this way 😦

Dell Latitude E5500 and Magic SysRq

November 17, 2009 3 comments

At work I’m using the Dell Latidude E5500 notebook, running on Debian testing. Today, I had some issues with Xorg which could not detect my keyboard and mouse, so I tried to do the Magic SysRq tricks (you can read about it at Wikipedia). Unfortunatley, to press SysRq (on F10), I had to use the Fn key, so if I pressed e. g. Alt+Fn+SysRq+U, the U was detected as keypad 4 because of the Fn key. Luckily, it works as intended if you release the Fn key after having pressed Fn+SysRq, so to remount all mounted filesystems in read-only mode, you would actually hold Alt, hold Fn, hold SysRq, release Fn, press U.

Never thought notebook keyboards were so smart 🙂

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Sync your Windows Mobile 5/6 PDA with your Linux PC

October 30, 2009 Leave a comment

I recently bought a new (ok, a rather old ;-)) PDA, and I got used to the calendar and task features in Windows Mobile. Of course, I also wanted to synchronise all the tasks, appointments, contacts and files with my PC, but whatever I tried, it didn’t work somehow on my Ubuntu 9.04 machine… So, I’ve got it now: I had do blacklist the ipaq kernel module which wrongly handled the PDA when I plugged it in (i. e. edit /etc/modprobe.d/blacklist.conf and insert the line blacklist ipaq), and then the manual from suddenly worked like a charm 🙂

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netcat, your friendly network sniffer

September 24, 2009 1 comment

I was bored today and started to play around with this Windows Mobile Messaging application (I think it’s called Outlook Mobile or sort of thing), and I found out that I was not able to connect to my IMAP mailbox on my root server, though it worked with my Freemail account. So I wanted to see what makes Outlook Mobile bother about my IMAP server.

If you are familiar with Linux (which I suppose you are ;-)), you certainly know netcat. With this little tool, you can talk directly to servers on a byte-oriented basis, and this can be very useful if you have to debug programs which use character-oriented protocols like IMAP, SMTP, IRC and so on.

But I’ve realised that I can not only use netcat to talk to a server myself, but even to build a transparent proxy server that displays all the data that comes over it. After a while — okay, it was about 2 hours — I got the following nice command:

$ mkfifo pipe
$ tty=`tty`; netcat -l 1234 < pipe | tee $tty | netcat 143 | tee pipe

I could now set up Outlook Mobile to talk to port 1234 on my home computer and the bytes went straight to my console and also to port 143 (the IMAP port) on my server.

The first direction was straightforward: the first netcat process listens to the local port and pipes its output first to the console (using tee) and then to a second netcat instance that does the communication with the remote server. Now, the commands from the server have to get back to the client, so I created a named pipe using mkfifo (of course, your filesystem has to support it, so you better not do this on FAT) and used this as the input to the first netcat process that sends it back to the original client.

Of course, I could have used Wireshark, but I hate that it does not allow to copy&paste the contents of a packet so I have only the bytes of the protocol that I need — which can be quite useful if you want to reuse parts of the content, especially in character-oriented protocols. Also, the filter settings in Wireshark can be annoying, there is no simple way to only have packets from one network connection (or I haven’t found it yet).

So, finally I found out that is has something to do with the IMAP capabilities that Outlook Mobile bothers about. I suppose I will write something about it if I have traced the problem back.

Update: Note: You can also rewrite the server and/or client messages using sed, but be sure to use unbuffered output with -u like that:

tty=`tty`; netcat -l 143 < pipe | tee $tty | netcat 143 | sed -u 's/^\* CAPABILITY.*/* CAPABILITY IMAP4 STARTTLS/' | tee pipe

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