Should spice-vdagent be installed on host and service running?

[CaffeineAddict]

Using KVM/QEMU and virt-manager for virtualization
I installed spice-vdagent into guest system

When I run spice-vdagent in guest system for first time in fresh installation it hangs until I also run spice-vdagent in host system.
Upon reboot of the guest spice-vdagent command runs fine in guest, without needing for the command to be run in host as well.
When spice-vdagent command is run this starts the spice-vdagentd service.

I've read several tutorials and none of them say I need spice-vdagent on host system.
Do I need it on host system?
Do I need spice-vdagentd service to be running on host? (it's started not by systemctl but with spice-vdagent command)

How does spice-vdagent work between host and guest, if only guest needs it, why? and how that works?

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Beside this question, I have problem dragging files from guest to host but not vice versa.
copy/paste files and directories does not work both ways.

Do I miss anything and why it doesn't work.

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Software installed on host:

sudo apt install virt-manager
# Also installs virtinst and in turn qemu-utils,
# qemu-system-x86 and in turn libvirt-clients, libvirt-daemon, qemu-system-gui, swtpm, swtpm-tools, ovmf
sudo apt install openvswitch-switch # Also installs openvswitch-common
sudo apt install fuse3 guestfs-tools # Includes guestmount
# Also installs virt-p2v and squashfs-tools
sudo apt install ovmf swtpm swtpm-tools spice-vdagent
sudo apt install -t bookworm-backports qemu-system-x86 # Also installs libvirt-clients

Software installed in guest:

sudo apt install qemu-guest-agent
sudo apt install spice-vdagent

 

[PuppyHome]

Should be installed within the GUEST OS.

Link.

 

[CaffeineAddict]

Should be installed within the GUEST OS.

Link.

I already followed that tutorial but 2nd part of it does not work.

But just now I also found this:

Is spice-vdagent required for Wayland?

I noticed the following message in syslog: Cannot access vdagent virtio channel /dev/virtio-ports/com.redhat.spice.0 I am running Ubuntu 18.10 on Wayland, so could I delete spice-vdagent? And...

askubuntu.com

Anyway IDK why can't I drag items from guest to host. and why copy/paste items doesn't work.