Unfortunately, I have never played with Lin_guider using its remote access method. But, I would suggest you load Lin_guider, its cccd firmware for the cameras, and run the program independently of KStars, first. If it works ok, then, the problem is with KStars.
If not, you most likely have firewall, UDP setting, permissions, or port assignment issue. I have used KStars and Lin_guider separately with no problems. I would suggest separate desktops for each works very conveniently. If one of the software then crashes, its very easy to recover. i.e. KStars crash while guiding. One can simply restart KStars, connect and sync.