Web Server on Embedded System

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Hello,

I am currently implementing a web server application on a ARM-based
embedded system. The requirement is to able to access and control the
devices on the board through a web interface. The board runs on eCOS.

How do I go about creating a web interface for the devices? I read
that a few popular webserver available such as BOA, tthttpd and
GoAhead webserver. Which one will be good for this purpose?

Thanks in advance for your advices!

Re: Web Server on Embedded System
You have to
1. right a driver that performs the low level accesses
2. generate CGI code to call the driver that can be accessed from the
webserver
3. generate web pages with control/status data form CGI

The book at http://www.embeddedlinuxinterfacing.com/ provides a good example
of this.

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Re: Web Server on Embedded System
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All this is good advice for an embedded Linux system, but...


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    ^^^^^^^^^^^^^^^^^^^^^^

.. I'm not sure if any of this applies to eCOS.

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Does eCOS even have tasks in the sense that Linux does (i.e. processes
in seperate address spaces, fork(), etc.)? If not, then I suspect
that some, maybe all of these web servers will not run on eCOS.

Rob

--
Robert Kaiser                     email: rkaiser AT sysgo DOT com
SYSGO AG                          http://www.elinos.com
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Re: Web Server on Embedded System

Hi Robert,

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eCos has threads, but not processes.  The goahead web server runs on
eCos, but I don't know about the others.  eCos is certainly a different
environment than Linux, and this must be take into consideration.

http://ecos.sourceware.org/docs-2.0/ref/net-httpd-chapter.html

Ciao,
Dave

Re: Web Server on Embedded System

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If you don't mind a basic question, how does a thread
differ from a process?

Steve

Re: Web Server on Embedded System
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Each process has it's own address space that is distinct and protect from
that of other processes.  Threads share a single address space.

--
Grant Edwards                   grante             Yow!  .. I want a COLOR
                                  at               T.V. and a VIBRATING BED!!!
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Re: Web Server on Embedded System


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Thanks, that makes sense.

S.


Re: Web Server on Embedded System
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With that CLinux would not have processes :-(

I suppose it's more the intended use: with multiple threads you _want_
to use common memory locations, while with multiple processes you always
use system means to move information from one process to another.

-Michael

Re: Web Server on Embedded System

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This is correct. uCLinux does not have real processes.

Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88   Web: www.denx.de
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Re: Web Server on Embedded System
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[See Grant Edward's good explanation]

Specific to the discussion of Web servers it is important to note that
the usual method for web servers to invoke CGI scripts is by running
them as sub-processes (usually through fork()). (Often, CGI scripts
are written in Perl, so a perl interpreter gets invoked to interpret
a perl script). Obviously, if an OS lacks processes, CGI scripts
won't work so easily.

Actually, I would like to know how the goahead web server implements
CGI script execution.

Rob

--
Robert Kaiser                     email: rkaiser AT sysgo DOT com
SYSGO AG                          http://www.elinos.com
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Re: Web Server on Embedded System

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The GoAhead web server doesn't do CGI at all.

Instead, it allows you to attach C functions to specific URLs
(typically the ones used by forms to submit data) to handle
what would be done by a CGI application in apache.  There is a
set of C-callable functions to retrieve the values of variables
submitted by the form.  The server is single-threaded, so no
other requests can be handled while the form-handler function
is active.

--
Grant Edwards                   grante             Yow!
                                  at              
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Re: Web Server on Embedded System

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You write HTML?

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It depends on your requirements, which you neglected to state.

I've used GoAhead under eCos and it worked well.

If you want useful answers you're going to have to ask better
questions.  This is a linux newsgroup, BTW, and you'd be far,
far, better off asking eCos questions on the eCos mailing
list.

I suggest you read this to start with:

  http://www.catb.org/~esr/faqs/smart-questions.html

--
Grant Edwards                   grante             Yow!  I'm a nuclear
                                  at               submarine under the
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Re: Web Server on Embedded System
McObject has released an in-memory embedded web server that would be
appropriate.  It has a (much) smaller footprint than e.g. GoAhead.

http://www.mcobject.com/extremews.shtml


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Re: Web Server on Embedded System
Thanks for the advices guys. I guess I wanted a quick overview idea of
howta go about doing it. Frankly, requirement given to me is just as
vague. Perhaps after going thru everything more throughly I can ask
more precise qns. Thanks!

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Re: Web Server on Embedded System
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You might consider Run-Time-Access as the interface to the low
level program.  It is described at http://www.runtimeaccess.com .



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