Well, first, xhost needs to be run as the user actually owning the running x-server. All you're doing is trying to change the root user's x permissions, for a server that doesn't exist.
Second, running xhost+ is very insecure. You're allowing everyone access to the x-server. At the very least limit it to only the hosts and users you actually want to give access to it. Even better is to set up an xauthority "handshake" for the systems involved.
Third, the default configuration for the x-server in many distros is set to ignore tcp requests (it's started with "--nolisten-tcp"). You may need to restart the x-server without it.
Finally, check to see if there isn't some kind of firewall blocking the requests.