Well, with your "-serial" setup, you've put the guest serial console on the telnet port, so there is nothing to switch on the host console here via the CTRL-a c key combination, i.e. this is the expected behavior. What exactly were you trying to do here? Access the serial console via two ways, one time via telnet and one time via the host console? AFAIK that's not possible.
** Changed in: qemu Status: New => Invalid -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1713328 Title: Unable to C-a in -nographic if -serial telnet Status in QEMU: Invalid Bug description: qemu-system-i386 (version 2.6.1, running on Linux/x86_64) started with: qemu-system-i386 -m 64M -machine type=pc -rtc base=localtime,clock=host -nographic -serial telnet:127.0.0.1:1234,server,nowait -net nic,model=ne2k_pci -net user,hostfwd=tcp:127.0.0.1:2200-:22,tftp=/ does not accept the escape key (C-a) to perform functions such as switching from monitor to console. Verified both in GNU screen and in the Linux console. If '-serial telnet:127.0.0.1:1234,server,nowait' is removed from the command line, the escape key is accepted (and Qemu doesn't enter the monitor immediately). To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1713328/+subscriptions