adafruit · tannewt · Feb 25, 2026 · Feb 11, 2026 · Feb 25, 2026
diff --git a/.gitignore b/.gitignore
@@ -113,3 +113,7 @@ TAGS
 
 # git-review-web outputs
 .review
+
+# Zephyr trace files
+**/channel0_0
+**/*.perfetto-trace
diff --git a/locale/circuitpython.pot b/locale/circuitpython.pot
@@ -2067,10 +2067,13 @@ msgstr ""
 
 #: ports/espressif/common-hal/socketpool/SocketPool.c
 #: ports/raspberrypi/common-hal/socketpool/SocketPool.c
-#: ports/zephyr-cp/common-hal/socketpool/SocketPool.c
 msgid "SocketPool can only be used with wifi.radio"
 msgstr ""
 
+#: ports/zephyr-cp/common-hal/socketpool/SocketPool.c
+msgid "SocketPool can only be used with wifi.radio or hostnetwork.HostNetwork"
+msgstr ""
+
 #: shared-bindings/aesio/aes.c
 msgid "Source and destination buffers must be the same length"
 msgstr ""

diff --git a/ports/zephyr-cp/Makefile b/ports/zephyr-cp/Makefile
@@ -8,8 +8,7 @@ BUILD ?= build-$(BOARD)
 
 TRANSLATION ?= en_US
 
-
-.PHONY: $(BUILD)/zephyr-cp/zephyr/zephyr.elf flash recover debug run clean menuconfig all clean-all test fetch-port-submodules
+.PHONY: $(BUILD)/zephyr-cp/zephyr/zephyr.elf flash recover debug run run-sim clean menuconfig all clean-all test fetch-port-submodules
 
 $(BUILD)/zephyr-cp/zephyr/zephyr.elf:
 	python cptools/pre_zephyr_build_prep.py $(BOARD)
@@ -36,6 +35,16 @@ debug: $(BUILD)/zephyr-cp/zephyr/zephyr.elf
 run: $(BUILD)/firmware.exe
 	$^
 
+run-sim:
+	$(MAKE) BOARD=native_native_sim BUILD=build-native_native_sim build-native_native_sim/firmware.exe
+	truncate -s 2M build-native_native_sim/flash.bin
+	mformat -i build-native_native_sim/flash.bin ::
+	@if [ -d CIRCUITPY ] && [ -n "$$(find CIRCUITPY -mindepth 1 -print -quit)" ]; then \
+		echo "Populating build-native_native_sim/flash.bin from ./CIRCUITPY"; \
+		mcopy -s -i build-native_native_sim/flash.bin CIRCUITPY/* ::; \
+	fi
+	build-native_native_sim/firmware.exe --flash=build-native_native_sim/flash.bin --flash_rm -wait_uart -rt
+
 menuconfig:
 	west build --sysbuild -d $(BUILD) -t menuconfig
 

diff --git a/ports/zephyr-cp/README.md b/ports/zephyr-cp/README.md
@@ -28,6 +28,20 @@ make BOARD=nordic_nrf7002dk
 This uses Zephyr's cmake to generate Makefiles that then delegate to
 `tools/cpbuild/build_circuitpython.py` to build the CircuitPython bits in parallel.
 
+## Running the native simulator
+
+From `ports/zephyr-cp`, run:
+
+```sh
+make run-sim
+```
+
+`run-sim` starts the native simulator in realtime.
+It prints the PTY path to connect to the simulator REPL.
+If a local `./CIRCUITPY/` folder exists, its files are used as the simulator's CIRCUITPY drive.
+
+Edit files in `./CIRCUITPY` (for example `code.py`) and rerun `make run-sim` to test changes.
+
 ## Testing other boards
 
 [Any Zephyr board](https://docs.zephyrproject.org/latest/boards/index.html#) can

diff --git a/ports/zephyr-cp/bindings/hostnetwork/HostNetwork.c b/ports/zephyr-cp/bindings/hostnetwork/HostNetwork.c
@@ -0,0 +1,37 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2026 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#include "bindings/hostnetwork/HostNetwork.h"
+
+#include "py/runtime.h"
+
+//| class HostNetwork:
+//|     """Native networking for the host simulator."""
+//|
+//|     def __init__(self) -> None:
+//|         """Create a HostNetwork instance."""
+//|         ...
+//|
+static mp_obj_t hostnetwork_hostnetwork_make_new(const mp_obj_type_t *type,
+    size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    mp_arg_check_num(n_args, n_kw, 0, 0, false);
+
+    hostnetwork_hostnetwork_obj_t *self = mp_obj_malloc(hostnetwork_hostnetwork_obj_t, &hostnetwork_hostnetwork_type);
+    common_hal_hostnetwork_hostnetwork_construct(self);
+    return MP_OBJ_FROM_PTR(self);
+}
+
+static const mp_rom_map_elem_t hostnetwork_hostnetwork_locals_dict_table[] = {
+};
+static MP_DEFINE_CONST_DICT(hostnetwork_hostnetwork_locals_dict, hostnetwork_hostnetwork_locals_dict_table);
+
+MP_DEFINE_CONST_OBJ_TYPE(
+    hostnetwork_hostnetwork_type,
+    MP_QSTR_HostNetwork,
+    MP_TYPE_FLAG_NONE,
+    make_new, hostnetwork_hostnetwork_make_new,
+    locals_dict, &hostnetwork_hostnetwork_locals_dict
+    );
diff --git a/ports/zephyr-cp/bindings/hostnetwork/HostNetwork.h b/ports/zephyr-cp/bindings/hostnetwork/HostNetwork.h
@@ -0,0 +1,19 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2026 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <stdint.h>
+
+#include "py/obj.h"
+
+typedef struct {
+    mp_obj_base_t base;
+} hostnetwork_hostnetwork_obj_t;
+
+extern const mp_obj_type_t hostnetwork_hostnetwork_type;
+
+void common_hal_hostnetwork_hostnetwork_construct(hostnetwork_hostnetwork_obj_t *self);
diff --git a/ports/zephyr-cp/bindings/hostnetwork/__init__.c b/ports/zephyr-cp/bindings/hostnetwork/__init__.c
@@ -0,0 +1,26 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2026 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#include "py/obj.h"
+
+#include "bindings/hostnetwork/__init__.h"
+#include "bindings/hostnetwork/HostNetwork.h"
+
+//| """Host networking support for the native simulator."""
+//|
+
+static const mp_rom_map_elem_t hostnetwork_module_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_hostnetwork) },
+    { MP_ROM_QSTR(MP_QSTR_HostNetwork), MP_ROM_PTR(&hostnetwork_hostnetwork_type) },
+};
+static MP_DEFINE_CONST_DICT(hostnetwork_module_globals, hostnetwork_module_globals_table);
+
+const mp_obj_module_t hostnetwork_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t *)&hostnetwork_module_globals,
+};
+
+MP_REGISTER_MODULE(MP_QSTR_hostnetwork, hostnetwork_module);
diff --git a/ports/zephyr-cp/bindings/hostnetwork/__init__.h b/ports/zephyr-cp/bindings/hostnetwork/__init__.h
@@ -0,0 +1,11 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2026 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include "bindings/hostnetwork/HostNetwork.h"
+
+extern hostnetwork_hostnetwork_obj_t common_hal_hostnetwork_obj;
diff --git a/ports/zephyr-cp/boards/frdm_rw612.conf b/ports/zephyr-cp/boards/frdm_rw612.conf
@@ -20,6 +20,7 @@ CONFIG_MBEDTLS_PKCS1_V15=y
 CONFIG_MBEDTLS_KEY_EXCHANGE_RSA_ENABLED=y
 CONFIG_MBEDTLS_ENTROPY_C=y
 CONFIG_MBEDTLS_CTR_DRBG_ENABLED=y
+CONFIG_MBEDTLS_SHA1=y
 CONFIG_MBEDTLS_USE_PSA_CRYPTO=n
 
 CONFIG_BT=y

diff --git a/ports/zephyr-cp/boards/native/native_sim/autogen_board_info.toml b/ports/zephyr-cp/boards/native/native_sim/autogen_board_info.toml
@@ -49,7 +49,8 @@ frequencyio = false
 getpass = false
 gifio = false
 gnss = false
-hashlib = false
+hashlib = true # Zephyr networking enabled
+hostnetwork = true # Zephyr board has hostnetwork
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false
@@ -87,7 +88,7 @@ rtc = false
 sdcardio = true # Zephyr board has busio
 sdioio = false
 sharpdisplay = true # Zephyr board has busio
-socketpool = false
+socketpool = true # Zephyr networking enabled
 spitarget = false
 ssl = false
 storage = true # Zephyr board has flash

diff --git a/ports/zephyr-cp/boards/native/nrf5340bsim/autogen_board_info.toml b/ports/zephyr-cp/boards/native/nrf5340bsim/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/native_sim.conf b/ports/zephyr-cp/boards/native_sim.conf
@@ -18,3 +18,19 @@ CONFIG_I2C_EMUL=y
 CONFIG_EEPROM=y
 CONFIG_EEPROM_AT24=y
 CONFIG_EEPROM_AT2X_EMUL=y
+
+CONFIG_NETWORKING=y
+CONFIG_NET_IPV4=y
+CONFIG_NET_TCP=y
+CONFIG_NET_SOCKETS=y
+CONFIG_ETH_NATIVE_TAP=n
+CONFIG_NET_DRIVERS=y
+CONFIG_NET_SOCKETS_OFFLOAD=y
+CONFIG_NET_NATIVE_OFFLOADED_SOCKETS=y
+CONFIG_HEAP_MEM_POOL_SIZE=1024
+
+CONFIG_NET_LOG=y
+
+CONFIG_MBEDTLS=y
+CONFIG_MBEDTLS_SHA1=y
+CONFIG_MBEDTLS_SHA256=y
diff --git a/ports/zephyr-cp/boards/nordic/nrf5340dk/autogen_board_info.toml b/ports/zephyr-cp/boards/nordic/nrf5340dk/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/nordic/nrf54h20dk/autogen_board_info.toml b/ports/zephyr-cp/boards/nordic/nrf54h20dk/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/nordic/nrf54l15dk/autogen_board_info.toml b/ports/zephyr-cp/boards/nordic/nrf54l15dk/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/nordic/nrf7002dk/autogen_board_info.toml b/ports/zephyr-cp/boards/nordic/nrf7002dk/autogen_board_info.toml
@@ -49,7 +49,8 @@ frequencyio = false
 getpass = false
 gifio = false
 gnss = false
-hashlib = false
+hashlib = true # Zephyr networking enabled
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/nxp/frdm_mcxn947/autogen_board_info.toml b/ports/zephyr-cp/boards/nxp/frdm_mcxn947/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/nxp/frdm_rw612/autogen_board_info.toml b/ports/zephyr-cp/boards/nxp/frdm_rw612/autogen_board_info.toml
@@ -49,7 +49,8 @@ frequencyio = false
 getpass = false
 gifio = false
 gnss = false
-hashlib = false
+hashlib = true # Zephyr networking enabled
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/nxp/mimxrt1170_evk/autogen_board_info.toml b/ports/zephyr-cp/boards/nxp/mimxrt1170_evk/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/renesas/da14695_dk_usb/autogen_board_info.toml b/ports/zephyr-cp/boards/renesas/da14695_dk_usb/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/renesas/ek_ra6m5/autogen_board_info.toml b/ports/zephyr-cp/boards/renesas/ek_ra6m5/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/renesas/ek_ra8d1/autogen_board_info.toml b/ports/zephyr-cp/boards/renesas/ek_ra8d1/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/st/nucleo_n657x0_q/autogen_board_info.toml b/ports/zephyr-cp/boards/st/nucleo_n657x0_q/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/st/nucleo_u575zi_q/autogen_board_info.toml b/ports/zephyr-cp/boards/st/nucleo_u575zi_q/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/st/stm32h7b3i_dk/autogen_board_info.toml b/ports/zephyr-cp/boards/st/stm32h7b3i_dk/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/boards/st/stm32wba65i_dk1/autogen_board_info.toml b/ports/zephyr-cp/boards/st/stm32wba65i_dk1/autogen_board_info.toml
@@ -50,6 +50,7 @@ getpass = false
 gifio = false
 gnss = false
 hashlib = false
+hostnetwork = false
 i2cdisplaybus = true # Zephyr board has busio
 i2cioexpander = false
 i2ctarget = false

diff --git a/ports/zephyr-cp/common-hal/hostnetwork/HostNetwork.c b/ports/zephyr-cp/common-hal/hostnetwork/HostNetwork.c
@@ -0,0 +1,15 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2026 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#include "bindings/hostnetwork/HostNetwork.h"
+
+hostnetwork_hostnetwork_obj_t common_hal_hostnetwork_obj = {
+    .base = { &hostnetwork_hostnetwork_type },
+};
+
+void common_hal_hostnetwork_hostnetwork_construct(hostnetwork_hostnetwork_obj_t *self) {
+    (void)self;
+}
diff --git a/ports/zephyr-cp/common-hal/hostnetwork/HostNetwork.h b/ports/zephyr-cp/common-hal/hostnetwork/HostNetwork.h
@@ -0,0 +1,11 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2026 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include "bindings/hostnetwork/HostNetwork.h"
+
+extern hostnetwork_hostnetwork_obj_t common_hal_hostnetwork_obj;