had same problem with xhost / -display with X running on fedora core 2. (I..e X server running on fedora box was disallowing incoming X traffic).
In brief: On fedora core 2 add "DisallowTCP=false" to /etc/X11/gdm/gdm.conf
In your case therefore, 1) on LOCALHOST make the above moficiation. 2) Reboot just to be sure (I'm sure there's a better way, but it's quick enough). 3) get X running again on LOCALHOST & do xhost REMOTEHOST, 4) check whether it works with xterm -display LOCALHOST on the Sun.
Credit to the guy the sender who posted
http://fedoranews.voisinage.com/index.php?p=10 (in French). Translation FYI:
> Avec la Red Hat 9, permetter l’accès à un autre X-Window système était possible avec ‘xhost +machin’. Mais le serveur X de la Fedora Core n’écoute pas sur le port TCP 6000, ainsi ‘machin’ ne peut pas ouvrir de nouvelles fenêtres.
With red hat 9, allowing access to another X-window system was possible with ‘xhost +machin’. But the X server of the Fedora Core does not listen on the TCP 6000 port, thus "someone" cannot open new windows.
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> Dand le fichier de configuration gdm.conf de Fedora, l’action suivante est commentée: “DisallowTCP=true”, le problème c’est que l’action est vraie par défaut. Positionner “DisallowTCP=false” devrait résoudre votre problème.
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In the configuration file gdm.conf of Fedora, the following action is commented: "DisallowTCP=true”, the problem being that the action is true by default. To position (? to add in the right location?) “DisallowTCP=false” should solve your problem.
Phillip