QEMU

Download an executable from https://github.com/espressif/qemu.

Use the esp32-qemu envelope which has the "openeth" driver included.

Start an ethernet provider:

import esp32.net.ethernet as esp32
import net.ethernet

   provider := esp32.EthernetServiceProvider.mac-openeth
       --phy-chip=esp32.PHY-CHIP-DP83848
   provider.install
   network ::= ethernet.open
...

Use toit tool firmware extract --format=image (or format=qemu for older versions).

Run qemu as follows:

qemu-system-xtensa -M esp32 -nographic \
   -drive file=IMAGE_FROM_ABOVE,format=raw,if=mtd \
   -nic user,model=open_eth,hostfwd=tcp::9000-:9000 \
   -s