this problem has plagued me for years: some computers running krfb respond VERY slowly to input - about 5 seconds. It's strange, I've always assumed that if something ran on one computer it would run on another, but i'd estimate that krfb runs n 8 out of 10 computers i try to use it on, on the troublesome computers, it always has the same symptom: a 5 to 10 second delay in response to input. the slow computers do not show any other symptoms, the cpu isn't loaded, the replacement and/or elimination of all network equipment (except the installed network cards) makes no difference, I've tried replacing the video card too, I've never been able to identify ANYTHING that affects the problem (except using a different computer!). Reproducible: Always Steps to Reproduce: 1. absolutely reproducible on some computers. 2. 3. Actual Results: some computers wont respond in a reasonable time to input received over krfb. Expected Results: krfb should respond at about the same speed on all computers.
I observe a similar behavior with KDE/Plasma session when the remote computer's monitor is turned off. As soon as I switch the monitor on, full speed is restored. Do you use KDE/Plasma on the remote computers? Is the monitor on or off on the remote computers?