I's my first time installing Linux/Apache.
I loaded CentOS and LAMPP on a machine attached to a LAN.
Turned off http and mysql (because I didn't want conflict with LLAMPP)
chkconfig httpd off
chkconfig mysqld off
then successfully LAMPP started with 
/opt/lampp/lampp start
Starting XAMPP for Linux 1.7.3a...
XAMPP: Starting Apache with SSL (and PHP5)...
XAMPP: Starting MySQL...
XAMPP: Starting ProFTPD...
XAMPP for Linux started.
Problem: Unable to connect - Firefox can't establish a connection to the server at 179.16.51.36.
I need some pointers as to where to look next.
No errors in error_log file (just some warnings)
I can ping server.
httpd.conf looks like this:
ServerRoot "/opt/lampp"
Listen 80
ServerAdmin 
[email protected]
ServerName 179.16.51.36
DocumentRoot "/opt/lampp/htdocs"
<Directory />
    Options FollowSymLinks
    AllowOverride None
</Directory>
<Directory "/opt/lampp/htdocs">
    Options Indexes FollowSymLinks ExecCGI 
Includes
    Order allow,deny
    Allow from all
</Directory>
ErrorLog logs/error_log
LogLevel warn
<IfModule log_config_module>
    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%h %l %u %t \"%r\" %>s %b" common
    <IfModule logio_module>
      LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
    </IfModule>
    CustomLog logs/access_log common
</IfModule>
<IfModule alias_module>
    ScriptAlias /cgi-bin/ "/opt/lampp/cgi-bin/"
</IfModule>
<IfModule cgid_module>
</IfModule>
<Directory "/opt/lampp/cgi-bin">
    AllowOverride None
    Options None
    Order allow,deny
    Allow from all
</Directory>
DefaultType text/plain
<IfModule mime_module>
    TypesConfig etc/mime.types
    AddType application/x-compress .Z
    AddType application/x-gzip .gz .tgz
    AddHandler cgi-script .cgi .pl
    AddType text/html .shtml
    AddOutputFilter 
INCLUDES .shtml
</IfModule>
EnableMMAP off
EnableSendfile off