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In my previous post regarding OpenVPN, I assumed that the machine is already running iptables as a gateway. If the machine is just a standalone server, you have to enable NAT gateway in iptables. In order to do that, modify /etc/sysconfig/iptables to follow below sample.

*nat
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -i tun+ -j ACCEPT
-A INPUT -i tap+ -j ACCEPT  

Once you have a server and want to work like you sit in front of the console, you are looking for VPN. I have set many VPN on Linux servers. There are so many solutions and standards. Anyway, most of them rely on the standard and UDP protocol. UDP is good for tunneling but might not work correctly behide NAT and firewall. Usually, all networks allow to access web through web proxy. The web protocol, HTTP, relies on TCP protocol. OpenVPN is a VPN solution which supports both UDP and TCP at the same time. Cool! You can even establish VPN connection through HTTP proxy.

As of today, everyone knows what BitTorrent is with no doubt. To download/upload via BitTorrent, you need a kind of BitTorrent client. Lots of BitTorrent client has been developed during two years ago. BTQueue is one of them. Anyway, it seems The Big Three are sharing the biggest part of BitTorrent client in the wild.

1. uTorrent 1.5
2. BitComet 0.63

What is your favorite web application framework? There are so many choices. Jet Propulsion Labs release a movie to present the review process of 5 frameworks. Thanks greggles to share that url. Below are the list of that frameworks.

• JBoss
• Ruby on Rails - Creating a weblog in 15 minutes

If you are very busy and mostly forget what you planed, you might want some kind of calendar software. As far as I know, web-based calendar will never work because it is on the web. You may forget to open that page to see what to do next. And most of all, you have to go on-line every time you just want to see the calendar. In addition, you want a host to place your calendar software, e.g., WebCalendar.

As a result, the best solution is a desktop calendar software. One of the best is Microsoft Outlook. Anyway, my favorite mail client is Thunderbird so Outlook is not my choice at all. Sunbird seems to be okay but unfortunately, it doesn’t support Buddhism Era, 2006 is 2549, at all. I live until to day without calendar and now I think it is the time to choose again.

Have you ever want to know what exactly happens during view a web page? If you are a web programmer, system programmer, or even hacker, you must have ever seen something being transmitted out of your machine and their responses. I am talking about the basic part to debug a web application. Basically, there are 2 basic choices to request a web page; GET and POST. Then data in your machine are encoded and sent to the web server via these request and get response, the web page, back. However, today technology is not as easy as I stated earlier. There are something about headers, cookies, content-type, and many more. You might get strange behavior due to incorrectly set cookie or assign wrong content-type. In this situation, you will be so happy if you know what are sent and received during the session. It is very useful information for all of us.