Archive for the ‘network’ Category

set up a proxy server for yourself

January 5, 2015 Leave a comment

You want to have a US proxy for yourself. For instance, you want to listen to Pandora Radio, but its home page tells you “sorry peasant, you don’t live on the holy US soil“.

Here I explain one possible way. Create a droplet at Digital Ocean (it costs $5 a month). When you create the droplet, select a US location.

Create the droplet, configure the SSH access.

Then, install squid, which is a full featured web proxy cache server.

To start using your proxy, install the FoxyProxy Firefox add-on and configure it.

Now, if you visit, you will notice that behind the proxy your real IP is still visible! You are not anonymous (yet).

To hide behind your proxy, we need some more configurations. Edit “/etc/squid3/squid.conf” and add these lines:

via off
forwarded_for off

request_header_access Allow allow all 
request_header_access Authorization allow all 
request_header_access WWW-Authenticate allow all 
request_header_access Proxy-Authorization allow all 
request_header_access Proxy-Authenticate allow all 
request_header_access Cache-Control allow all 
request_header_access Content-Encoding allow all 
request_header_access Content-Length allow all 
request_header_access Content-Type allow all 
request_header_access Date allow all 
request_header_access Expires allow all 
request_header_access Host allow all 
request_header_access If-Modified-Since allow all 
request_header_access Last-Modified allow all 
request_header_access Location allow all 
request_header_access Pragma allow all 
request_header_access Accept allow all 
request_header_access Accept-Charset allow all 
request_header_access Accept-Encoding allow all 
request_header_access Accept-Language allow all 
request_header_access Content-Language allow all 
request_header_access Mime-Version allow all 
request_header_access Retry-After allow all 
request_header_access Title allow all 
request_header_access Connection allow all 
request_header_access Proxy-Connection allow all 
request_header_access User-Agent allow all 
request_header_access Cookie allow all 
request_header_access All deny all

Restart the squid server:

sudo service squid3 start

Visit again. It will indicate your proxy’s IP, stating that no proxy is detected :) Cool.

At the moment anybody can use your proxy if they find out your IP:port combination. I tried to add username / password HTTP authentication but it didn’t work. If someone has a step-by-step guide for that, let me know.

Categories: network Tags: , ,

don’t use free proxy servers

January 4, 2015 Leave a comment

Why are free proxies free?

because it’s an easy way to infect thousands of users and collect their data

When you download a page via a proxy server, there is no guarantee that you get the original page… There is a high risk that the proxy server sent you back a modified page. Read the article above for more details.

Categories: network, security Tags: , ,

copy large files between computers at home over the network

January 2, 2015 Leave a comment

I have a desktop machine at home with a Windows 2007 virtual machine. I mainly have it because of Powerpoint. Recently I prefer to work on my laptop in the living room. Today I needed Powerpoint, so I decided to copy the whole Windows virtual machine and put it on my laptop. The only problem is that it was 67 GB and I didn’t have that much space on my external HDDs :(

Don’t panic. On my desktop machine I entered the folder that I wanted to copy and started a web server:

python -m SimpleHTTPServer

With “ifconfig” I checked the local IP address of the machine, it was

On my laptop I opened a browser and navigated to ““. All the files I needed were there. Since I’m lazy and I didn’t want to click on each link one by one, I issued the following command (tip from here):

wget -r --no-parent

The download speed was about 10 MB/sec, so it took almost 2 hours.

Categories: network, python Tags: , ,

VirtualBox: accessing the guest from the host

September 23, 2013 Leave a comment

In a VirtualBox guest machine I wanted to set up a web server for testing purposes. How to access the guest’s web server from the host?

In the guest’s network settings, normally you already have a NAT network adapter. This way the guest can access the Internet.

But how to establish a network communication between the host and the guest? In the guest’s network settings, select the tab “Adapter 2”. At home “Bridged Adapter” worked for me.

However, at my workplace “Bridged Adapter” didn’t work. After some research I wanted to try “Host-only Adapter”, but I ran into a difficulty. I couldn’t add a host-only adapter, I got the following error message: “no host-only network adapter selected”. And the GUI didn’t offer anything in the dropdown list :(


Fortunately I found the solution here. The image above was also borrowed from

For future references, I quote the steps here:

Probably, the virtual host-only network wasn’t set up yet. Here’s is how you can fix this:

  1. From the main menu, select File > Preferences (Ctrl+G) – NOT the settings of a single vm
  2. Select Network in the list on the left
  3. You should see an empty white box with “Host-only Networks” at the top. On the right, there are three buttons to manage them. Click the topmost one (with a green plus symbol). A new Host-only network will be created and added to the list.

Normally, the settings of the new network will be ok, but for completeness, I give the default values here. You can access the settings for the host-only network through the screwdriver button on the right.

  • Adapter:
    • IPv4 address:
    • IPv4 Network Mask:
  • DHCP server:
    • Enable server: checked
    • Server Address:
    • Server Mask:
    • Lower Address Bound:
    • Upper Address Bound:

You can change these settings to your liking, as long as they’re consistent.

Thanks to Bert Van Vreckem for this great answer.

Guest’s IP address
Executing “ifconfig” in the guest, you’ll get its IP address. Mine is under “eth1”, next to “inet addr:”. Try to ping the guest from the host and vice versa. They should work :)

Categories: network Tags: , , ,

What is my IP address?

October 20, 2011 4 comments

You want to figure out your IP address.

New way
Visit Google and type in “what is my ip“, or just simply “my ip“. Direct link:

Old way

Sexy way

This tip is from here (in Hungarian).

Categories: google, network Tags:

Who is hosting a given website?

March 9, 2011 1 comment

To find out who is hosting a given website, visit


Related work

You can also install the Flagfox Firefox add-on. Then, with a simple click you can get lots of information about the current page you are visiting.

Categories: firefox, network Tags: , ,

Is a given website down or not?

March 9, 2011 1 comment


Your favorite website doesn’t want to load. Is the given website down? Or is there a temporary problem with your network provider?


Try the website Normally they check your site from three random stations around the world. If 2 or more stations find an error or do not get response within 4 seconds, the site is considered to be “down”.

Tip: on the main page of Down Or Not, there is a cloud with the most popular searches. Check out the cloud to find out what’s hot today…

Other methods
Some alternative methods:

  • ping HOST
  • traceroute HOST

Where HOST is the site you want to check. However, these two methods are not too reliable for checking if a website is up. I just checked a site that was definitely up, but both ping and traceroute failed to reach it.

Categories: network Tags: , , ,

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