This section contains information on different http server software packages and additional server side tools like script languages for CGI programs etc. There are several dozen web servers, I only covered those that are fully functional. As some of these are commercial products, I have no way of trying them. Most of the information in the overview section was pieced together from various web sites. If there is any incorrect or missing information please let me know.
For a technical description on the http mechanism, take a look at the RFC documents mentioned in the chapter "For further reading" of this HOWTO.
I prefer to use the Apache server. It has almost all the features you would ever need and its free! I will admit that this section is heavily biased toward Apache. I decided to concentrate my efforts on the Apache section rather than spread it out over all the web servers. I may cover other web servers in the future.
This was the first web server. It was developed by the European Laboratory for Particle Physics (CERN). CERN httpd is no longer supported. The CERN httpd server is reported to have some ugly bugs, to be quite slow and resource hungry. The latest version is 3.0. For more information visit the CERN httpd home page at http://www.w3.org/Daemon/Status.html. It is available for download at ftp://sunsite.unc.edu/pub/Linux/apps/www/servers/httpd-3.0.term.tpz (no it is not a typo, the extension is actually .tpz on the site; probably should be .tgz)
The NCSA HTTPd server is the father to Apache (The development split into two different servers). Therefore the setup files are very similar. NCSA HTTPd is free and the source code is available. This server not covered in this document, although reading the Apache section may give you some help. The NCSA server was once popular, but most people are replacing it with Apache. Apache is a drop in replacement for the NCSA server(same configuration files), and it fixes several shortcomings of the NCSA server. NCSA HTTPd accounts for 4.9% (and falling) of all web servers. (source September 1997 Netcraft survey). The latest version is 1.5.2a. For more information see the NCSA website at http://hoohoo.ncsa.uiuc.edu.
Apache is the king of all web servers. Apache and its source code is free. Apache is modular, therefore it is easy to add features. Apache is very flexible and has many, many features. Apache and its derivatives makes up 44% of all web domains (50% if you count all the derivatives). There are over 695,000 Apache servers in operation (source November 1997 Netcraft survey).
The official Apache is missing SSL, but there are two derivatives that fill the gap. Stronghold is a commercial product that is based on Apache. It retails for $995; an economy version is available for $495 (based on an old version of Apache). Stronghold is the number two secure server behind Netscape (source C2 net and Netcraft survey). For more information visit the Stronghold website at http://www.c2.net/products/stronghold/. It was developed outside the US, so it is available with 128 bit SSL everywhere.
Apache-SSL is a free implementation of SSL, but it is not for commercial use in the US (RSA has US patents on SSL technology). It can be used for non-commercial use in the US if you link with the free RSAREF library. For more information see the website at http://www.algroup.co.uk/Apache-SSL/.
Fast Track was developed by Netscape, but the Linux version is put out by Caldera. The Caldera site lists it as Fast Track for OpenLinux. I'm not sure if it only runs on Caldera OpenLinux or if any Linux distribution will do (E-mail me if you have the answer). Netscape servers account for 11.5% (and falling) of all web servers (source September 1997 http://www.netcraft.com/survey/). The server sells for $295. It is also included with the Caldera OpenLinux Standard distribution which sells for $399 ($199.50 educational). The web pages tell of a nice administration interface and a quick 10 minute setup. The server has support for 40-bit SSL. To get the full 128-bit SSL you need Netscape Enterprise Server. Unfortunately that is not available for Linux :( The latest version available for Linux is 2.0 (Version 3 is in beta, but its not available for Linux yet). To buy a copy goto the Caldera web site at http://www.caldera.com/products/netscape/netscape.html For more information goto the Fast Track page at http://www.netscape.com/comprod/server_central/product/fast_track/
WN has many features that make it attractive. First it is smaller than the CERN, NCSA HTTPd, an Apache servers. It also has many built-in features that would require CGI's. For example site searches, enhanced server side includes. It can also decompress/compress files on the fly with its filter feature. It also has the ability to retrieve only part of a file with its ranges feature. It is released under the GNU public license. The current version is 1.18.3. For more information see the WN website at http://hopf.math.nwu.edu/.
AOLserver is made by America Online. I'll admit that I was surprised by the features of a web server coming from AOL. In addition to the standard features it supports database connectivity. Pages can query a database by Structured Query Language (SQL) commands. The database is access through Open Database Connectivity (ODBC). It also has built-in search engine and TCL scripting. If that is not enough you can add your own modules through the c Application Programming Interface (API). I almost forgot to mention support for 40 bit SSL. And you get all this for free! For more information visit the AOLserver site at http://www.aolserver.com/server/
Zeus Server was developed by Zeus Technology. They claim that they are the fastest web server (using WebSpec96 benchmark). The server can be configured and controlled from a web browser! It can limit processor and memory resources for CGI's, and it executes them in a secure environment (whatever that means). It also supports unlimited virtual servers. It sells for $999 for the standard version. If you want the secure server (SSL) the price jumps to $1699. They are based outside the US so 128 bit SSL is available everywhere. For more information visit the Zeus Technology website at http://www.zeus.co.uk. The US website is at http://www.zeus.com. I'll warn you they are cocky about the fastest web server thing. But they don't even show up under top web servers in the Netcraft Surveys.
CL-HTTP stands for Common Lisp Hypermedia Server. If you are a Lisp programmer this server is for you. You can write your CGI scripts in Lisp. It has a web based setup function. It also supports all the standard server features. CL-HTTP is free and the source code is available. For more information visit the CL-HTTP website at http://www.ai.mit.edu/projects/iiip/doc/cl-http/home-page.html (could they make that url any longer?).
If you have a commercial purpose (company web site, or ISP), I would strongly recommend that you use Apache. If you are looking for easy setup at the expense of advanced features then the Zeus Server wins hands down. I've also heard that the Netscape Server is easy to setup. If you have an internal use you can be a bit more flexible. But unless one of them has a feature that you just have to use, I would still recommend using one of the three above.