there are a few things in your post which irritate me.
The client Spark always connects to a XMPP server (like Wildfire), and this server may offer transports to MSN, ICQ, …
Spark does not connect to a webserver, but of course to a domain name like “jabber.org”.
If you want to setup a public XMPP server then continue reading.
While setting up Wildfire you did specify a domain name like “jabber.mycompany.tld” or just “mycompany.tld”. Wildfire binds to all available ip addresses unless other configured.
So maybe you need to change the servername (Server Properties, xmpp.domain).
Depending on where you did install Wildfire you probably only need to talk to your firewall administrator to get the ports opened and forwarded to your server.
Also in LAN environments you should use a DNS name and not the ip address to connect.