Before starting this Ethernet project the author did of course some prototyping and then he noticed alreadythat UDP was not a problem with lots of space left on the atmega88. Therefore he was quite confident that TCP + HTTP will work. TCP/IP was invented more than 25 years ago. Todays microcontrollers provide almost the computing power a standard computer had at that time. No java or xml was used at that time. Things were done in smart and efficient ways.

As you can imagine this web-server code is written for a friendly environment. Don’t put it on the open internet. The code uses e.g the incoming packet to build from it the outgoing packet. An attacker who sends a mal formed IP packet might be able to confuse the TCP/IP stack. The code is verified with a lot of different browsers and a number of operating systems. It was tested Linux, BSD Unix, Win 98, Win XP, Mac OS-X with a number of different web browsers. It works very well but it was not tested agains atacks and destroy tests.

Webserver Based On ATMega88: [Link] – [via]

Interfacing an Analog-to-Digital Converter (ADC) with Linux via the parallel port is fairly simple. There two major areas that need to be addressed – hardware and software. The hardware consists of the parallel port, an ADC, and an analog signal source. The software we programmed in ‘C’ language.

Interfacing Your Computer to an ADC via the Parallel Port: [Link]

Zigbee, formally IEEE 802.15.4, is another short-range radio standard that uses the 2.4 GHz “microwave oven” band, alongside wireless Ethernet and Bluetooth. Compared to these others, Zigbee is most suited for low-power applications involving simple microcontrollers, for example wireless sensing, home and industrial automation, and so on. Its basic parameters are a data rate of up to 250 kbits/s and a typical range of 50 m.A small Linux box like the NSLU2 (aka Slug: 266 MHz XScale ARM processor, filesystem on a USB flash drive, takes about 5W, runs Debian GNU/Linux and other distributions) could be useful in a Zigbee deployment. For example, an always-on Slug could be responsible for logging data sent by remote sensors, and generating graphs on web pages, sending email alerts and so on.

SlugBee – Adding Zigbee Radio to a Slug: [Via] – [Link]

It will be available in about 600 stores, as well as online, Wal-Mart said. A comparable Everex PC preinstalled with Windows Vista Home Basic and more memory costs $298 partly because the manufacturer has to pay Microsoft Corp. for a software license, so I think people will like the new computer and discover the goods of linux.

Both computers come with keyboard, mouse, and speakers, but without a monitor. As you already may know Linux is developed and offered on a open-source basis by individuals and companies around the world.

It’s being used especially on servers because of its high stability on long term use. The variant of Linux on the gPC is called gOS and is derived from the popular Ubuntu variant. It’s mostly oriented toward Google’s Web sites and online applications, like YouTube, Gmail and the company’s word processing program, all of which can be used only when the computer is connected to a broadband line.

The PC comes with a dialup modem, but gOS doesn’t support it. So most users likely will get online using other ways. Google’s entrance to the OS market is relatively new and I think gOS will be a great chance for users who would like to move away from Microsoft and windows to something new and better.

Wal-Mart spokeswoman Melissa O’Brien said it is stocking the computer in about one in eight stores to test the demand for an open-source product. The gPC has a low-end processor from VIA Technologies, plus 512 megabytes of internal memory, an 80-gigabyte hard drive and a combination DVD drive and CD burner. Everex says the processor is very energy efficient, meriting the “Green” part of the name.

here is a screenshot of the gPC or you could call it a gOS screenshot:

Sources :

http://www.thinkgos.com

http://www.everex.com

http://www.walmart.com

Also if you would like to see more gOS screenshots you should check this article of mine.

iptables -A PREROUTING -t nat -p tcp -i eth0 –dport 88 -j DNAT –to 192.168.1.2:22

after entering this command debian1 will forward any request on port 88 from eth0 to 192.168.1.2 on port 22. Now all I have to do is to enter 1.1.1.1 port 88 in putty and I can log-in to debian2 trough ssh. That’s it short and simple about port forwarding.

#This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
address 1.1.1.2
netmask 255.255.255.0
network 1.1.1.255
broadcast 1.1.1.255
gateway 1.1.1.1
dns-nameservers 1.1.1.1
dns-search .com
hwaddress ether 00:01:04:1b:2C:1F

Open this file in your favorite editor. I use nano. You can see that my ip address is 1.1.1.2 and my gateway is 1.1.1.1 instead of these in your file you will see your network settings. Now, under the last line of the interfaces file you have to add the following

hwaddress ether 00:01:04:1b:2C:1F

replacing 00:01:04:1b:2C:1F with the mac you want to assign to the interface where you are adding the line. Now save the file with ctrl+x then y to confirm and restart the network service with
/etc/init.d/networking restart
Now type ifconfig and there it is you should see the mac you entered earlier assigned to eth0 (if you choused eth0). You’re done the mac will now load every time the network load’s.

date –set 2007-10-15
to set yyyy-mm-dd
date –set 16:47:30
to set hh-mm-ss
hwclock –systohc
to sync hardware clock to what we introduced earlier

    At least from Debian version 2.2 onwards, the system automatically saves the system time to hardware clock on shutdown, and sets the system clock from hardware clock when Debian boots up. This is done in the script /etc/init.d/hwclock.sh.

    Another thing you might ran into is changing the timezone.
If the timezone is not set or is wrong, log in as superuser and run tzconfig to configure the timezone.

That’s it a short tutorial about date in Debian.

For the method described below I’m using apt for installing snmp, so before you start this you should configure apt and add some http or ftp sources into your /etc/apt/sources.list or if you have your installation dvd/cd you can use that. Let’s get started:

We need to install snmpd package using the following command:
apt-get install snmpd

    That’s it snmpd is installed, now we move on to the config part. We will edit /etc/snmp/snmpd.conf. This is the main config file for snmpd so before doing any changes you should take a copy of this file in case anything goes wrong with this command:
cp /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.orig
next open file for edit with:
nano /etc/snmp/snmpd.conf

Now for local access only you should change
#com2sec paranoid default public
com2sec readonly default public
#com2sec readwrite default private
To
#com2sec paranoid default public
com2sec readonly default public
#com2sec readwrite default private

Notice “public” this will be our community. If you want to interrogate the snmp service from another server you should change:
#com2sec paranoid default public
com2sec readonly default public
#com2sec readwrite default private
To
#com2sec paranoid default public
com2sec local localhost public
com2sec mynetwork 1.1.1.1 public
#com2sec readwrite default private
(replace “1.1.1.1” with the ip of the remote server)
you also need to add these line to /etc/snmp/snmpd.conf
group MyROGroup v1 mynetwork
group MyROGroup v2c mynetwork
group MyROGroup usm mynetwork

Next step in remote interrogating is to edit /etc/default/snmpd with
nano /etc/default/snmpd
and remove the 127.0.0.1 bit.

Next step, is optional, if you want to personalize a bit your snmpd you can edit this:
syslocation Unknown (configure /etc/snmp/snmpd.local.conf)
syscontact Root <root@localhost> (configure /etc/snmp/snmpd.local.conf)
to something like
syslocation Main Datacenter
syscontact webmaster@yourdomain.com
Now we need to restart the snmp service to activate the new settings.
/etc/init.d/snmpd restart

Your snmp server is now active and running.

    A list of common commands is very useful when new to Debian, to teach you how to handle/manage files and systems.I extracted from Debian’s User Reference Manual the most often used commands :

Commands for reading documentation:

man [section-number] subject
man shows the manual page on the command (use q or ctrl-C to get out of it if it doesn’t terminate at the end of the text)
This command is crucial for helping you learn how to use it and other Linux commands

info [subject]
A lot of Debian Linux documentation is provided in info format. This is similar to a hypertext format, in that you can jump to other sections of the documentation by following links embedded in the text.

help [subject]
Use help for on-line help about bash’s built-in commands. Help by itself prints a list of subjects for which you can ask for help.

Commands for basic file-handling:

If you are gonna use linux as operating system you have to know this commands:
pwd
Show the current directory.

cd [directory]
Change your current directory to the named directory. If you don’t specify directory, you will be returned to your home directory.

mkdir new_directory
mkdir is used to create a new directory. new_directory can be specified as a path, or as a simple name (in which case it is created in the current directory).

mv source target
mv moves source file to target and deletes source; source can be a list of files, but in that case target must be a directory.This is also the way to rename a file or directory.

cp source target
cp copies source to target. Again, target can be a directory and source a list of files.

ln source target
ln links source to target with hard or symbolic links according to the options.

rm filelist
rm deletes files. With the -r option it can delete directories and their contents.Be very careful with rm; once a file is deleted, you cannot get it back. There is no undelete command.

rmdir directorylist
rm deletes empty directories.

chmod mode filelist
chmod changes the permissions of files and directories. The mode is either an octal number, such as 644, or a symbolic representation of it, such as u=rw,go=r.

chown owner[.group] filelist
chown changes the ownership of files. Use the -R option to do this for an entire directory tree.

If .group is specified as well as owner, the group ownership of the files is changed as well.

chgrp group filelist
chgrp changes the group ownership of files. Use the -R option to do this for an entire directory tree.

ls directory
ls lists the contents of directory; by default, the output is sorted.There are more options to ls than to any other command. Those most commonly used are -l, to show the file permissions and the latest change date and -a, to show hidden dot-files.

Commands for managing file-systems:

df
df lists mounted partitions and shows the amount of space present, used and available. (The partitions will probably include /proc, which is a special `non-existent’ partition, that contains information about the current state of the Linux kernel.)

mount [partition directory]
mount by itself lists mounted partitions.It is also the command to use to add a partition’s file-system into the universal directory tree. For example:
mount /dev/hda2 /usr
You have to be superuser (log in as root or run su) in order to mount or unmount file-systems.

umount directory
umount removes a partition’s file-system from the universal directory tree. For example:
umount /usr

You have to be superuser (log in as root or run su) in order to mount or unmount file-systems.

Commands for Looking at files:

cat textfile[s]
cat dumps textfile[s] to screen without paging (like DOS’s type). If you name more than one file, each will be sent in order, with no break or heading.

more textfile[s]
more lists the textfile[s] to the screen in pages so that you can read it. Press Space-bar to move on one page, Enter to move on one line, and b to move back one page. Use q or ctrl-c to quit; more will quit automatically when it gets to the end of the last file.

less textfile[s]
less is like more but has more features and somewhat different behaviour. You have to type Q to terminate it.

head textfile[s]
head is used to see the first few lines of a file (by default, it shows 10 lines).

tail textfile[s]
tail is used to see the last few lines of a file (by default, it shows 10 lines).so for example if you want to see live your apache access.log file to see who is accessing your website you can type
tail -f /var/log/apache2/access.log

find directory -name filename
find tells you where filename is in the tree starting at directory. This command has many other useful options.

grep pattern filelist
grep scans each file in filelist for lines which match pattern

file file
file reports what kind of thing file is.

type file
type says where to find file in your search path.

whereis file
whereis is like type, but gives more information.

Commands for Session management:

exit or logout
Use exit or logout to terminate your session and log out. All jobs you have started are terminated, unless they were started with nohup, and your screen should return you to the log-in prompt. You can often use Ctrl-D to do the same, but that capability can be disabled.

su
Use su to become superuser. You will be asked to enter a password; this is the password for the root login.Becoming superuser is almost the same as logging in as root. You get the same power to do damage. Be very careful!

Use exit, logout or ctrl-D to stop being superuser.

bg and fg
If you are running one job and want to run something else in the same screen without stopping the first job, you can put the first job in the background by typing Ctrl-Z. You can then run other commands. You can start the first job running again in the background by using bg. It will continue to run in the background until it wants to send anything to the screen; then it will stop and wait. You can bring it forward again and let it continue by using the command fg.

script file
Use script to record everything that appears on the screen (until the next exit) in file. This is useful if you need to record what’s going on in order to include it in your message when you ask for help. Use exit, logout or ctrl-D to stop the recording session.

ps
Use ps to list your processes.
You can also use ps to see all processes on the system:
ps -ax
The number in the column headed PID is the identifying number of the process. Under column TT is the tty (screen or window identifier) where it is running. A question mark here means that it is not attached to any screen or window, but is running in the background.

tty
tty shows you which terminal (screen or window) you are in.
tty
/dev/ttyp4

These commands relate to your identity as a user and the machine’s own identity:

passwd
Use passwd to change the password that you use when you log in. Follow the instructions on screen about what kind of password to choose. When you type the password in, it doesn’t show on the screen, so you have to enter it twice, to ensure that you make no typing errors.

id
id tells you what user you are and what group you are in.

id
uid=1000(olly)gid=1000(olly)groups=1000(olly),6(disk),20(dialout),25(floppy),26(tape),29(audio),34(backup),37
(operator),101(priory)
uid indicates your user number, gid your group number (which will be assigned to files that you create) and groups lists the other groups that you are a member of.

who -u
who -u reports everyone who is logged on.

uname -a
uname -a reports the name, type and operating system of your machine.

date
date reports the current time and date.
The superuser can use this command to set the date and time.

 Commands for Turning off the computer:

Turning the computer on and off is really a system administration subject, but I include it here because it is something that every user who is his own administrator needs to know. If someone else is responsible for administering the machine, you should neither need nor be able to shut it down.

shutdown -t 0 -h now
This command shuts the computer down safely. You can also use ctrl-alt-del if your system is set up for that. (If you are in X, ctrl-alt-del will be intercepted by X. Get out of X first by using ctrl-alt-backspace.) Never turn off a Unix machine without doing a safe shutdown: if you do, you will damage your file-systems.

This was extracted from Debian User Reference Manual.

    Under Linux the MAC address of a network card can be changed by doing the following under a root account.

/etc/init.d/networking stop

ifconfig eth0 hw ether 02:01:02:03:04:08

/etc/init.d/networking start

” 02:01:02:03:04:08” being the new assigned mac.

    Under Fedora Core 5, and possibly in other Linux distributions, to disable and restart networking, you must stop and start /etc/init.d/network, instead of /etc/init.d/networking. Using the described method your MAC address will revert to original MAC address (hardware MAC) after reboot. So if you want to make the change permanently in Debian you have to add

hwaddress ether 02:01:02:03:04:08

into the appropriate section of /etc/network/interfaces so that the MAC address is set when the network device is started.

You can also use the tool MACChanger to change the MAC address under Linux.