In my case the problem is quite subtle. Nearly every time we send the key strokes, the guest os keeps receiving space or tab or new line character. And ending part of the text is truncated, where the truncated part is fixed depending on the keystrokes we are sending. Additionally, the keystrokes are mis-ordered at a higher frequency than 1 out of a few hundreds as you said.
In brief, - Repeatedly receiving space, tab or new line character as ending - Truncation regarding ending part of key strokes - characters are mis-ordered, lost, repeated A question is, how can you make character transaction faster with vncdotool? In my case, vncdotool is typing fairly slow. I found this debian bug report quite useful, what do you think? https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=758881 Re-producing procedures --- I re-produced the problem in a slightly different way since your method seems not working for me. > qemu-img create tumbleweed.img 40G > qemu-system-x86_64 -drive file=tumbleweed.img,if=virtio -boot d -cdrom > openSUSE-Tumbleweed-DVD-x86_64-Snapshot20181119-Media.iso -m 2048 > --enable-kvm -display vnc=:1 > qemu-system-x86_64 -drive file=tumbleweed.img,if=virtio -m 4G --enable-kvm > -display vnc=:1 ** Bug watch added: Debian Bug tracker #758881 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=758881 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1802465 Title: typing string via VNC is unreliable Status in QEMU: New Bug description: QEMU version is 3.0.0 # Description The problem is that, when typing string through VNC, it can be unreliable -- sometimes some key strokes get skipped, sometimes get swapped, sometimes get repeated. There's no problem when typing through VNC on physical hardware. # Steps to reproduce 1. Launch virtual machine by: qemu-kvm -display vnc=:1 -m 2048 opensuse-leap-15.qcow2 2. Connect to VNC by: vncviewer -Shared :5901 3. Simulate a series of key strokes by "vncdotool" [1]: vncdotool -s 127.0.0.1::5901 typefile strings_to_be_typed.txt 4. Usually after a few hundred keys are typed, something goes wrong. I attached a screenshot that it mistypes " hello" to "h ello". [1] https://github.com/sibson/vncdotool To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1802465/+subscriptions