is 10.0.0.4 really your server name (xmpp.domain)? I wonder if a configuration based on IP addresses is supported by the plugin, a lot of things tend to NOT work while using the IP address instead of the xmpp.domain.
Evidently the server is running in 10.0.0.4 since it is responding to your requests. However, the forbidden error you are receiving may be triggered by any of these 2 cases (when Wildfire is configured so that anyone can see a user’'s presence):
The server name of your Wildfire server is not 10.0.0.4 but something else. The jid and req_jid parameters should be using your server name in the user’'s domain JID. Eg. admin@myserver.com
If your server name is 10.0.0.4 then crisan@10.0.0.4 is not a registered user.