Common vlan with no host privileges

[Narcis Garcia]

In a Debian 12 host (Qemu 7.2.13), not using superuser privileges,
I launch VM1:
$ qemu-system-x86_64 -name "Windows XP" (...)
        -device rtl8139,netdev=net0
        -netdev user,id=net0,smb=/home/_all/public
        -netdev socket,id=vlan-winxp,mcast=230.0.0.1:1234
        -device rtl8139,netdev=vlan-winxp
and VM2:
$ qemu-system-x86_64 -name debian10
        -device rtl8139,netdev=net0
        -netdev user,id=net0,smb=/home/_all/public
        -netdev socket,id=vlan-winxp,mcast=230.0.0.1:1234
        -device virtio-net-pci,netdev=vlan-winxp

Then in guest VM1 first (default) NIC acquires address 10.0.2.15/24 and 
I configure manually second NIC to have address 192.168.139.1/24
In guest VM2 first (default) NIC also acquires address 10.0.2.15/24 and 
I configure manually second NIC to have address 192.168.139.139/24

From VM1 I ping to 192.168.139.139 with result "Timeout"
From VM2 I ping to 192.168.139.1 with result "Destination Host Unreachable"

My goal is to make a Windows XP (VM1) access old Samba in Debian 10 
(VM2), and VM2 accesses to host smb/qemu resource. Both guests should 
reach WAN/Internet through user net (virtual gateway 10.0.2.2)

My questions:
1. What do I need to add to command line so communications between 
guests works?
2. Is there some documentation about fd= and localaddr= parameters I 
found on web comments? What are they intended for?

Thank you.

--
Narcis Garcia