Simultaneous clients connection

Support multiple concurrent connections to a single spice server.

Status

This feature is still experimental, it is not expected to work correctly under different client bandwidths, although it should not crash the server.

To enable:

Using libvirt

Modify the xml definition of the virtual machine to use SPICE_DEBUG_ALLOW_MC environment variable:

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
....
  <qemu:commandline>
    <qemu:env name='SPICE_DEBUG_ALLOW_MC' value='1'/>
  </qemu:commandline>
</domain>

Using QEMU

export SPICE_DEBUG_ALLOW_MC=1

Launch qemu vm as usual.

The stdout will contain an additional line:

spice: allowing multiple client connections

You can then launch clients as usual. A second client connection will not disconnect any of the previous clients. There is no set limit. The behavior of each channel in multiple client mode:

inputs - shared. All clients can supply mouse and keyboard.
display - shared. All clients receive display updates.
cursor - shared. All clients receive cursor updates.
playback - first connection after no connections. To do: make it shared.
record - first connection after no connections. To do: make it shared.
smartcard - first connection after no connections. To do: make it shared.
usbredir - first connection after no connections. To do: make it shared.
agent - ?

NB: The main channel is not on that list because it isn't a user visible channel. Every client has it's own main connection.

NB: First connection after no connections: To receive this channel you will have to connect after explicitly disconnecting all the previous clients. Otherwise you will easily reach a situation where ''none'' of the clients have any of those channels:

connect A
connect B (A is connected)
disconnect A (B is still connected)
connect C

Now both B and C only have {inputs,display,cursor}, no one has any other (playback,cursor,smartcard) connection. Specifically, the server didn't advertise those channels to clients B and C.