With Microsoft Internet Explorer
in IE options->advanced options-> disable native xmlhttp compatibility
in IE options->security->internet->custom level-> allow data access for other domains
With all browsers, even IE
There is another system that only detects hosts up or down with a timeout system. This system try to load an image from a given host and port but if it is not possible in a given time it shows a message, but I think this is worse and with a lot of false positives. It works in Firefox and IE, but I think only is useful to detect hosts up but not ports open or closed.
C o m m e n t s : h i p e r n e s @ u s e r s . s o u r c e f o r g e . o r g