Category Archives: Network

All about networks

How to use a remote firewire port and transcode DV video locally with ffmpeg

Vhs_cassette_bottomI recently moved into another appartment and found some old VHS tapes I recorded years ago. As luck would have it, I got my hands on a VCR and a MiniDV camcorder with builtin ADC, so I can get analog video signals into the MiniDV camcorder. So all I needed was a computer with firewire or IEEE1394 port. The only computer I have that still has a firewire port is my server, so I hooked the VCR to the MiniDV and the MiniDV to my server.
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How to enable and use Wake on LAN this article I will describe how to enable Wake-on-LAN (WOL) and how to use it to start-up a system remotely. In order to use Wake-on-LAN your systems hardware and network driver needs to actually support this technology. You will also need to know the MAC address of the systems ethernet card.
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How to use an SSH connection as a SOCKS proxy this article I will describe how to use an SSH connection as a SOCKS proxy. This basically means that you can route the network traffic of any application or even your entire systems traffic through an SSH connection.
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How to install Privoxy and combine it with Tor

In this post I’ll show you how you can improve your privacy and anonymity while you are browsing on some websites. For this purpose I’ll use Privoxy and Tor. Privoxy is a non-caching web-proxy with filtering capabilities for enhancing privacy. Tor uses an overlay network of volunteers and relays your traffic through the Tor network to it’s destination. It also encrypts your data, so no Tor node (except the exit node) can read your data.

This is not a high-security setup, but it should improve your privacy and anonymity.

1. Privoxy
2. Tor
3. Combine Privoxy and Tor
4. Appendix
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How to set up a stateful firewall with iptables

My old post to set up a small rules set for iptables is deprecated so I decided to update this post and improve some rules.
This time I tested this iptables setup on my Raspberry Pi. I connected to my Pi via SSH and the first time I tested the rules order I locked myself out and I had to connect the monitor and keyboard to fix this. The rule order in this post worked for me to set everything up via SSH.

I also tried this setup on a virtual machine and made a screencast of it. You can find the video at the end of this post.

1. Kernel modules
2. Important Rules
3. Chain Policies
4. Port Rules
5. Logging
6. Saving Rules
7. Appendix (Script and video)
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How to install a CalDav and CardDav server using Radicale

During my time at the university I had lots of meetings, events and I couldn’t remember all these events, so I had to write them down. But we’re living in a digital world, so I wanted to keep all my appointments digitally. I tried Thunderbird Lightning and it is a great Add On. But I also wanted to synchronize all these events with my smartphone without using an external cloud, e.g. Google Calendar.

I wanted a small program with minimal dependencies to act as a server which is able to run on a Raspberry Pi. It doesn’t have to provide a web interface, because I can use Thunderbird or my smartphone to add, change or delete events. I found Radicale which is written in Python and has no dependencies. It supports the CalDav and CardDav protocol. That’s all I wanted so I gave it a try. My first impression was very good and it works great. Here are all steps I did to set up my own CalDav server with Radicale.

1. Installation of Radicale
2. Adding bcrypt support to Radicale (optional step)
3. Configure Radicale
4. Configure Thunderbird Lightning
5. Configure Android Calendar
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How to make diffs of SVN and Git files with vimdiff

Version control systems like Git or SVN have lots of advantages. One can easily fork a project or create a new branch to test new code. I use Git for all my programs, reports and for my thesis. But sometimes it is necessary to see the difference of two versions of a file. One can use git diff or svn diff but in my opinion the output of these tools are not very nice and it is not easy to see the difference of the files.
In this post I will show you how you can display the difference of two versions of a (SVN or Git) file. The tool I’ll use for this purpose is vimdiff. It’s also possible to use gvimdiff for graphical vim, just replace vimdiff with gvimdiff.
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How to create your own PKI with openssl

Today certificates are widely used to verify, authenticate a client/user or server, to encrypt or sign emails or to sign other types of objects (e.g. source code). You are using a certificate at the moment, due to the secure http (https) connection.
In this post I will show you how to create your own Root Certificate Authority (CA).

1. Create a self signed root certificate
2. Create a sub ca certificate
3. Create a server certificate
4. Create a user certificate
5. Generate a certificate revocation list
6. Revoke a certificate
7. Export a certificate to PKCS#12 format
8. Bash script to manage your own CA

I recommend to configure your openssl.cnf (located at /etc/ssl/openssl.cnf). This is the most annoying part, but it simplifies the next steps. You can find an example of an openssl.cnf I’ll use at the end of this post. Be careful at the policy_match section, this can be a problem while signing a certificate signing request.
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How to receive files via Bluetooth on Gnome3

In this post I will describe how to receive files via Bbuetooth on Gnome3. Strangely it is possible to send files from your PC to any other device, but it is not possible to receive files from other devices via bluetooth. Maybe that’s just the case for people with a minimal installation of Gnome3 like my self, however the solution for this problem is very simple.

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How to set up TOR from source

In this post I’ll show you how to set up TOR (The Onion Router). You can use TOR to surf anonymously but I recommend NOT to use services with logins which can be connected to your real identity, e.g. email, instant-messanger, etc. You don’t know how the TOR-exit node is configured.
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