A tiny web server in C
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README.md

nweb README for version 23

  1. Bug fixed - was duplicating errors in the nweb.log file

    • thanks to Kieran Grant for stopping this and pointing out the fix.
  2. Added support for favicon.ico - if nothing elase this will stop annoying errors in the log file. Most browsers on first encountering a webpage also ask for this file. The name mean favourite icon - Wikipedia has more on this. It is a tiny Bit Map image (normally called .bmp and BMP editors can be used to create one - I used Windows Paint) I uses a very simple 16x16 pixels and 256 colour to keep the size and complexity down. To add support I added .ico file extension to the allowed extensions data structure and the sample favicon.ico file. This is then displyed by the browser at the little graphic next to the URL. The one I made looks like this withe blue background. +---+ |n | |Web| +---+

  3. As 1) removed a few lines, I managed to add 2) and still stay at 200 lines.

The code: nweb23.c -- the source code version 23 client.c -- sample client end source code

nweb executable files for: AIX 6.1 TL7 fnd AIX 7 TL1 POWER Ubuntu 12.4 for x86_64 Intel/AMD 64 bit Ubuntu 12.4 for x86_32 Intel/AMD 32 bit Fedora 17 Linux for x86_64 Intel/AMD 64 bit OpenSUSE 12.1 for x86_64 Intel/AMD 64 bit Red Hat RHEL 6.3 for x86_64 Intel/AMD 64 bit SUSE SLES 11 for x86_64 Intel/AMD 64 bit Debian Squeeze for ARM on Raspberry Pi

Minimum test website index.html -- test very bascis web page nigel.jpg -- test image file favicon.ico -- the favourite icon bit map file


nweb README for version 22

The nweb download file includes:

README -- this file

This file contains lots of hints & tips on compiling and running the nweb code

nweb22.c

The 22 is the version number. nweb stands for Nigel's Web server but I some times call it a nano web server (i.e. very small).

This nweb is a web server that will respond to simple web browser requests for static files. This version is exactly 200 lines long. I started with a target 100 lines and it worked fine too but then added comments, file type checks, security checks, sensible directory checks and logging.

To compile this you need a basic C compiler use: cc nweb22.c -o nweb If you want it to run faster you could include optimisation: cc -O2 nweb22.c -o nweb

Then to run it as root for the test files:

  1. Place the index.html file and nigel.jpg in to a sensible directory Note: not any system directories like / or /tmp A director in /home would be a good idea - below we use /home/nigel/web

  2. Make these files readable chmod ugo+r /home/nigel/web

  3. Decide the port number Port number 80 is the web server default and assumed by web browsers. you might have to be the root user to use that port number. If the machine is already running a web server then it will probably be using port 80 so you can't us 80. I test using port 8181 but you have to make up your mind.

  4. Start the nweb server: /home/nigel/bin/nweb 80 /home/nigel/web or if using 8181 /home/nigel/bin/nweb 8181 /home/nigel/web

    If the program and files are all in /home/nigel/all You could use: cd /home/nigel/all rm -f nweb.log ./nweb 80 . ps -ef | grep nweb tail -f nweb.log

    See below for explanations for the rm, ps and tail

  5. Note that any suitable files in the directory 2nd argument above could be served by the nmon web server - so don't have anything secret in that directory!

  6. Use a browser to test it if using port 80 on a machine hostname of abc123.com browser to: http://abc123.com/index.html

    If using port 8181 http://abc123.com:8181/index.html

  7. Running nweb as a regualr user You can run nweb as a regular user on some operating systems but not all. I find using sudo works on some: sudo /home/nigel/bin/nweb 80 /home/nigel/web

If you try and the log file reports socect connections errors worth trying the 8181 port or higher numbers. This is because lower port numbers are reserved for root user use.

  1. VERY IMPORTANT nweb will behave like a daemon process, so it disconnects from the users command shell, goes into the back ground, closes input and output I/O & protects itself from you logging off.
    It will look like it stopped, when it is in fact still running in the background - check with ps -ef | grep nweb Also note you will not see errors or warnings messages
  • they go in the log file.

Look in the nweb.log file for problems starting up or browsers connecting and requesting pages with: cat nweb.log or: tail -f nweb.log

I find it good to remove the nweb.log before I start nweb or it is easy to get confused with previous error messages in the log.

  1. As nweb runs as a daemon process it will try to run forever and not conntected to your user or terminal session. Logging out will not effect it. To stop nweb you have to stop it by a KILL signal. Find the nweb process with: ps -ef | grep nweb Then use: kill -9 PID to stop the nweb process.

  2. nweb.log Log file - what to look for Good example Here is an edited down sample nweb.log file. Note the first line = "starting" looks good as there is no following error.


INFO: nweb starting:8181:8913126 INFO: request:GET /index.html HTTP/1.1 [[1KB of deleted request stuff here]]:2 INFO: SEND:index.html:2 INFO: Header:HTTP/1.1 200 OK Server: nweb/21.0 Content-Length: 239 Connection: close Content-Type: text/html

INFO: request:GET /nigel.jpg HTTP/1.1 [[1KB of deleted request stuff here]]:3 INFO: SEND:nigel.jpg:3 INFO: Header:HTTP/1.1 200 OK Server: nweb/21.0 Content-Length: 10184 Connection: close Content-Type: image/jpg

Bad example A failure to start due to the port number is not aallowed or in use looks like:

INFO: nweb starting:80:8323296 ERROR: system call:bind Errno=13 exiting pid=8323296


client.c

This client.c program is designed to fake being a web browser. It sends the expected requests to the web server over a network socket connection and displays the results as text rather than graphically displaying the results. In the code you will have to change the two lines as below to match your web server or nweb server.

/* YOU WILL HAVE TO CHANGE THESE TWO LINES TO MATCH YOUR CONFIG / #define PORT 8181 / Port number as an integer - web server default is 80 / #define IP_ADDRESS "192.168.0.8" / IP Address as a string */

The default is to request the /index.html from the web server. If you want to request another file then change the GET line as below:

char *command = "GET /index.html HTTP/1.0 \r\n\r\n" ;

To, for example:

char *command = "GET /nigel.jpg HTTP/1.0 \r\n\r\n" ;

Then compile the program with: cc client.c -o client

I save the output in to a file as putting a non-test file like .jpg to the terminal screen can cause chaos: client >output

Then edit the output file: vi output

In real life, the interaction of web browser and web server can be much more complex.

  1. The web browser can tell the web server about its name, version and capabilities.

  2. The web server can send complex file types line JavaScript or Java programs or other active components.

  3. They can maintain a longer connection over the socket for efficiency.

  4. Below is an example of my Firefox brower requesting an index.html file. I have added newline characters to make it readable - it is 1300 bytes long! I have no idea what most of it is about. You will have to read the The World Wide Web Consortium (W3C) at http://www.w3.org for all the details.

GET /index.html HTTP/1.1Host: myserver.home.com:80User-Agent: Mozilla/5.0 (W indows; U; Windows NT 5.1; en-GB; rv:1.9.2.28) Gecko/20120306 Firefox/3.6.28 (.NET CLR 3.5.30729)Ac cept: image/png,image/;q=0.8,/*;q=0.5Accept-Language: en-gb,en;q=0.5Accept-Encoding: gzip,defla teAccept-Charset: ISO-8859-1,utf-8; q=0.7,*;q=0.7Keep-Alive: 115Connection: keep-alive**Referer: http://myserver.uk.home.com:8181/index.html**Cookie: __utma=101107545.1790272076.1316019590.13289002 55.1328908680.164; __utmz=101107545.1328566199.157.46.utmcsr=t.co|utmccn=(referral)|utmcmd=referral| u tmcct=/iTJx4DO1; UnicaNIODID=ZBr8gm79vIG-XKeoGGb; W3SSO_ACCESS=abc.home.com; ISP=70fdfc95 d93011d783e4de784ea97766-70fdfc95d93011d783e4de784ea97766-f67749a8b899e8ceed7e940b8c4bf189; Prof ile=2000121913394303111032836125|EN|866|866.BDF|en-GB; _unam=693fb60-1337f162b72-11770d11-5; WLS intra_USERID=nigel@hotmail.com; ipcInfo=cc%3Duk%3Blc%3Den%3Bac%3Dall; iwm1p=214617669; bprememberme=nigel@ hotmail.com; EPSPROFILE=EE2355DFE16AE020BE6C62FCB6BF5602; DWPERM=Xa.2/Xb.Xzso3-U35t8RWKvqBreGaQMgsP_RG Fl1124oIt-L-OPJIdSautkBN0D4NUp9JLlpUqPqB6CWOo-pgrJwhxNvvSfPAajgetaA2MOYwHfQPXPTRG9zwOMMR57EHQtXhOy5Om yzanyZthvVClm6uxvbwh0isEQ2Mm_9g2l7NjcA3RJdjuLaB3qlljOmyVuhDjBkgdNEb3PgYcCpbiu1FUzXrhPalhgsbAj7NBkaY88 Yyg/Xc./Xd./Xf./Xg.1696801

I hope this has been instructive, thanks, Nigel Griffiths