Linux Notes: gSOAP on CentOS-7 (and higher)

1. The information presented here is intended for educational use by qualified computer technologists.
2. The information presented here is provided free of charge, as-is, with no warranty of any kind.

Introduction

Official gsoap instructions are provided only for UNIX and Windows.

The following instructions are specific to Linux (CentOS, RHEL, Rocky).

Installing gsoap

Many self-help sites instruct you to build a second copy of Apache from source files just so you can gain access to apxs (APache eXtenSion tool). While this is possible on UNIX or Linux and can make initial development easier, it is not necessary on Linux since most distros can add apxs to your system via the "httpd-devel" package.

caveat: yum is the package manager on CentOS-7 and RHEL-7. Starting with version 8, yum commands are translated into dnf commands

Installing mod_gsoap

• you just installed gsoap-devel but will find that you are still missing support for the Apache plugin: mod_gsoap
• a little investigation will show that you must use the exact mod_gsoap files associated with the files downloaded from your distro
  • CentOS-7: installed gsoap_2.8.16 which uses mod_gsoap-0.6 dated 2013-08-25
  • CentOS-8: installed gsoap_2.8.91 which uses mod_gsoap-0.9 dated 2019-08-18
  • CentOS-9: installed gsoap_2.8.111 which uses mod_gsoap-1.0 dated 2021-08-19
  • which you can download from here: https://src.fedoraproject.org/lookaside/extras/gsoap/ (zip files)
  • note that I have seen file content differences between various versions of mod_gsoap-0.6 so am assuming that "the maintainer was just plain sloppy" or "knew nothing about major and minor version numbers".
    This means you must not download mod_gsoap files from here https://sourceforge.net/projects/mod-gsoap/ because they are dated 2005-02-04
• once you have downloaded a gsoap zip file to your desktop, then use something like 7-zip to drill down the archive to here:
  gsoap_2.8.16.zip\gsoap-2.8\gsoap\mod_gsoap
  then copy (via drag-n-drop) the mod_gsoap folder onto your desktop. Opening this folder will produce a view similar to this one:
  • folder: gsoap_win
  • folder: mod_gsoap-0.6 (you might see different version numbers depending upon the kit)
  • file: README.txt
• use sftp to drag-n-drop sub-folder mod_gsoap-0.6 (or whatever you find) to Linux location $HOME/gsoap/apache (or wherever you are building your gsoap files)

Building mod_gsoap

caveats:

• apxs must always be run as root or sudo.
• you might not ever want to use the -a option ( apxs may change /etc/httpd/conf/httpd.conf )
• you might not want to use the -i option ( apxs could overwrite an existing module under /usr/lib64/https/modules/ )

[neil@kawc4n apache_20]$ sudo apxs -i -c mod_gsoap.c
/usr/lib64/apr-1/build/libtool --silent --mode=compile gcc -std=gnu99 -prefer-pic -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexcep
tions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic  -DLINUX -D_REENTRANT -D_GNU_SOUR
CE -pthread -I/usr/include/httpd  -I/usr/include/apr-1   -I/usr/include/apr-1   -c -o mod_gsoap.lo mod_gsoap.c && touch mod_gsoap.sl
o
mod_gsoap.c:57:0: warning: "TRUE" redefined [enabled by default]
 #define TRUE ((int)0xffff)
 ^
In file included from /usr/include/apr-1/apr_pools.h:45:0,
                 from /usr/include/apr-1/apr_strings.h:50,
                 from mod_gsoap.c:28:
/usr/include/apr-1/apr_general.h:55:0: note: this is the location of the previous definition
 #define TRUE (!FALSE)
 ^
mod_gsoap.c: In function 'SoapSharedLibrary_unload':
mod_gsoap.c:261:13: warning: unused variable 'nClose' [-Wunused-variable]
         int nClose = dlclose(This->m_hLibrary);
             ^
mod_gsoap.c: In function 'gsoap_handler':
mod_gsoap.c:927:11: warning: variable 'pszResponse' set but not used [-Wunused-but-set-variable]
     char *pszResponse = NULL;
           ^
mod_gsoap.c: At top level:
mod_gsoap.c:1303:24: warning: "/*" within comment [-Wcomment]
      "http://www.w3.org/*\//soap-envelope"},
 ^
mod_gsoap.c:1305:24: warning: "/*" within comment [-Wcomment]
      "http://www.w3.org/*\/soap-encoding"},
 ^
mod_gsoap.c:1307:24: warning: "/*" within comment [-Wcomment]
      "http://www.w3.org/*\//XMLSchema-instance"},
 ^
mod_gsoap.c:1309:24: warning: "/*" within comment [-Wcomment]
      "http://www.w3.org/*\//XMLSchema"},
 ^
mod_gsoap.c:438:1: warning: 'SoapSharedLibraries_clear' defined but not used [-Wunused-function]
 SoapSharedLibraries_clear(SoapSharedLibraries *This)
 ^
mod_gsoap.c:1142:13: warning: 'gsoap_child_init' defined but not used [-Wunused-function]
 static void gsoap_child_init(server_rec *s, apr_pool_t*p)
             ^
mod_gsoap.c:1155:13: warning: 'gsoap_child_exit' defined but not used [-Wunused-function]
 static void gsoap_child_exit(server_rec *s, apr_pool_t*p)
             ^
/usr/lib64/apr-1/build/libtool --silent --mode=link gcc -std=gnu99 -Wl,-z,relro,-z,now   -o mod_gsoap.la  -rpath /usr/lib64/httpd/mo
dules -module -avoid-version    mod_gsoap.lo
/usr/lib64/httpd/build/instdso.sh SH_LIBTOOL='/usr/lib64/apr-1/build/libtool' mod_gsoap.la /usr/lib64/httpd/modules
/usr/lib64/apr-1/build/libtool --mode=install install mod_gsoap.la /usr/lib64/httpd/modules/
libtool: install: install .libs/mod_gsoap.so /usr/lib64/httpd/modules/mod_gsoap.so
libtool: install: install .libs/mod_gsoap.lai /usr/lib64/httpd/modules/mod_gsoap.la
libtool: install: install .libs/mod_gsoap.a /usr/lib64/httpd/modules/mod_gsoap.a
libtool: install: chmod 644 /usr/lib64/httpd/modules/mod_gsoap.a
libtool: install: ranlib /usr/lib64/httpd/modules/mod_gsoap.a
libtool: finish: PATH="/sbin:/bin:/usr/sbin:/usr/bin:/sbin" ldconfig -n /usr/lib64/httpd/modules
----------------------------------------------------------------------
Libraries have been installed in:
   /usr/lib64/httpd/modules

If you ever happen to want to link against installed libraries
in a given directory, LIBDIR, you must either use libtool, and
specify the full pathname of the library, or use the `-LLIBDIR'
flag during linking and do at least one of the following:
   - add LIBDIR to the `LD_LIBRARY_PATH' environment variable
     during execution
   - add LIBDIR to the `LD_RUN_PATH' environment variable
     during linking
   - use the `-Wl,-rpath -Wl,LIBDIR' linker flag
   - have your system administrator add LIBDIR to `/etc/ld.so.conf'

See any operating system documentation about shared libraries for
more information, such as the ld(1) and ld.so(8) manual pages.
----------------------------------------------------------------------
chmod 755 /usr/lib64/httpd/modules/mod_gsoap.so
[neil@kawc4n apache_20]$ sudo find / -name mod_gsoap.so -exec ls -la {} \;
-rwxr-xr-x. 1 root root 83944 Mar  3 09:12 /home/neil/gsoap/apache/mod_gsoap-0.6/apache_20/.libs/mod_gsoap.so
-rwxr-xr-x. 1 root root 83944 Mar  3 09:12 /usr/lib64/httpd/modules/mod_gsoap.so
[neil@kawc4n apache_20]$

Editing /etc/httpd/conf/httpd/conf

<VirtualHost *:80>
	DocumentRoot "/var/www/html"
	ErrorLog "logs/kawc4n_80_error_log"
	AddType image/x-icon .ico
	...
	... snip ...
	...
	# ================================================================
	# I need this to serve up "index.html"
	#
	<Directory "/var/www/html">
            Options Indexes FollowSymLinks
            AllowOverride None
            Require all granted
        </Directory>
	# ================================================================
	ScriptAlias /cgi-bin/  "/var/www/cgi-bin/"
	# ================================================================
	#
	#	NSR gsoap experiments
	#
	# notes:
	# 1) this area is only for gsoap services run via plugin mod_gsoap (not executables run from cgi-bin)
	# 2) these gsoap services must have been built using 'apxs' (see my notes)
	# 3) the plugin mod_gsoap for Apache-2.x works differently than Apache-1.x
	# 4) <Location /soap> is used in the connect string like so: http://kawc4n.on.bell.ca/soap
	# 5) make sure calcserver3.so has privs which can be used by Apache
	# 6) reminders:
	# 6a apachectl configtest -AND- apachectl -l -AND- apachectl -M
	# 6b apachectl graceful -OR- apachectl restart
	# 6c systemctl status httpd.service
	# 7) requires mod_authz_core.so (loaded many lines before this place)
	#
	LogLevel debug
	LogLevel trace8
	LoadModule gsoap_module modules/mod_gsoap.so
        #<IfModule mod_gsoap.c>
	 <Location "/soap">
	  SetHandler gsoap_handler
	  SOAPLibrary /usr/lib64/httpd/modules/some-demo.so
	  #Require all granted
	  Order allow,deny
	  Allow from all
	 </Location>
	 <Location "/calcserver3">
	  SetHandler gsoap_handler
	  SOAPLibrary /usr/lib64/httpd/modules/calcserver3.so
	  #Require all granted
	  Order allow,deny
	  Allow from all
	 </Location>
	#</IfModule>
</VirtualHost>

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