HELP: ESP32s3 -> access mongoose webserver via USB NCM from PC

[imdahisaria]

Hello All,

First of all thank you very much for such a cool tool like mongoose. Using the webui was fun and very interesting. I used it successfully on my esp32 s3 via the Wifi.

I am now trying something new in my project and have reached a bottleneck and need some help.

Here are the details:

Hardware: ESP32s3 Devkitc v1.1

Description/ Task:

I have implemented tinyusb as network in NCM mode. The mongoose server is started.
I then want to connect the USB to my PC/ linux . The linux PC recognises the it as Ethernet.
All good so far.

Now when i open the browser and type 192.168.7.1 i expect to see the Mongoose dashboard but I dont.

Sharing the code and logs.

// lwIP → USB: transmit a frame to the PC
static esp_err_t usb_netif_transmit(void *h, void *buffer, size_t len)
{
	ESP_LOGI("usb_tx", "TX %d bytes", (int)len);
	return tinyusb_net_send_sync(buffer, (uint16_t)len, NULL, portMAX_DELAY);
}

static void usb_free_tx_cb(void *buffer, void *ctx) { /* no-op */ }

// USB → lwIP: frame received from PC
static esp_err_t custom_rx_interceptor(void *buffer, uint16_t len, void *ctx)
{
	ESP_LOGI("usb_rx", "RX %d bytes", (int)len);
	return esp_netif_receive(global_usb_netif, buffer, len, NULL);
}

// Called when USB host connects
static void usb_net_init_cb(void *ctx)
{
	ESP_LOGI("USB", "USB host connected");
	esp_netif_action_start(global_usb_netif, NULL, 0, NULL);
	esp_netif_action_connected(global_usb_netif, NULL, 0, NULL);
}

int app_main()
{
	esp_err_t ret = nvs_flash_init();
	if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND)
	{
		ESP_ERROR_CHECK(nvs_flash_erase());
		ret = nvs_flash_init();
	}
	ESP_ERROR_CHECK(ret);

	ESP_ERROR_CHECK(esp_netif_init());
	ESP_ERROR_CHECK(esp_event_loop_create_default());

	ESP_LOGI(TAG, "Init native USB");

	// 2. Driver config — transmit function MUST be set before action_start
	esp_netif_driver_ifconfig_t drv_cfg = {
		.handle = (esp_netif_iodriver_handle) "usb",
		.transmit = usb_netif_transmit,
		.transmit_wrap = NULL,
		.driver_free_rx_buffer = usb_free_tx_cb,
	};

	// 3. Base netif config — no DHCP server flag, static IP only
	esp_netif_inherent_config_t base_cfg = {
		.flags = ESP_NETIF_FLAG_AUTOUP,
		.if_desc = "usb_ncm",
		.if_key = "USB_NCM",
		.route_prio = 10,
	};

	esp_netif_config_t netif_cfg = {
		.base = &base_cfg,
		.driver = &drv_cfg,
		.stack = ESP_NETIF_NETSTACK_DEFAULT_ETH};

	global_usb_netif = esp_netif_new(&netif_cfg);
	assert(global_usb_netif);

	// 4. Set static IP
	esp_netif_ip_info_t ip_info = {};
	IP4_ADDR(&ip_info.ip, 192, 168, 7, 1);
	IP4_ADDR(&ip_info.gw, 192, 168, 7, 1);
	IP4_ADDR(&ip_info.netmask, 255, 255, 255, 0);

	esp_netif_dhcpc_stop(global_usb_netif); // stop DHCP client
	ESP_ERROR_CHECK(esp_netif_set_ip_info(global_usb_netif, &ip_info));

	// Confirm IP was set
	esp_netif_ip_info_t check = {};
	esp_netif_get_ip_info(global_usb_netif, &check);
	ESP_LOGI(TAG, "netif IP: " IPSTR, IP2STR(&check.ip));

	tinyusb_config_t tusb_cfg = TINYUSB_DEFAULT_CONFIG();
	ESP_ERROR_CHECK(tinyusb_driver_install(&tusb_cfg));

	tinyusb_net_config_t net_config = {
		.mac_addr = {0x02, 0x02, 0x84, 0x6A, 0x96, 0x00},
		.on_recv_callback = custom_rx_interceptor,
		.free_tx_buffer = usb_free_tx_cb,	 // void (*)(void *buffer, void *ctx)
		.on_init_callback = usb_net_init_cb, // void (*)(void *ctx)
		.user_context = NULL,
	};

	ESP_ERROR_CHECK(tinyusb_net_init(&net_config));

	esp_netif_action_start(global_usb_netif, 0, 0, 0);
	esp_netif_action_connected(global_usb_netif, 0, 0, 0);

	xTaskCreatePinnedToCore(mongoose_task, "mongoose_task", 10240, NULL, 4, NULL, 1);

	return 0;
}

inside mongoose_impl.c

void mongoose_poll(void)
{
  glue_lock();
  mg_mgr_poll(&g_mgr, 10);
#if WIZARD_ENABLE_WEBSOCKET
  send_websocket_data();
#endif
  glue_unlock();
}

void mongoose_task(void *arg)
{


  mg_mgr_init(&g_mgr);
  mg_log_set(MG_LL_DEBUG);

  // Start HTTP listener on port 8080
  mg_http_listen(&g_mgr, "http://0.0.0.0:80", http_ev_handler, &g_mgr);

  // Run only while flasg is true

  while (1)
  {
    mg_mgr_poll(&g_mgr, 50);
    // NO vTaskDelay here — or keep it to 1ms maximum
    vTaskDelay(pdMS_TO_TICKS(10));
  }

  ESP_LOGI("MONGOOSE TASK", "Shutting down Mongoose Server");

  mg_mgr_free(&g_mgr);

  vTaskDelete(NULL);
}

after running the code and starting the browser i see the following line

D (1115) esp_netif_lwip: esp_netif_update_default_netif_lwip 0x3fcecaf0
D (1115) esp_netif_lwip: call api in lwip: ret=0x0, give sem
I (1125) main_task: Returned from app_main()
1d6    3 mongoose.c:5845:mg_mgr_init    MG_IO_SIZE: 2048, TLS: builtin
1e0    3 mongoose.c:5762:mg_listen      1 48 http://0.0.0.0:80
I (1795) usb_rx: RX 42 bytes
I (1865) usb_rx: RX 42 bytes
I (1915) usb_rx: RX 42 bytes
I (1965) usb_rx: RX 42 bytes
I (1965) usb_rx: RX 54 bytes
I (2065) usb_rx: RX 183 bytes
I (2245) usb_rx: RX 131 bytes
I (2495) usb_rx: RX 131 bytes
I (2745) usb_rx: RX 131 bytes
I (2825) usb_rx: RX 54 bytes
I (2945) usb_rx: RX 119 bytes
I (3065) usb_rx: RX 183 bytes
I (3965) usb_rx: RX 42 bytes
I (4165) usb_rx: RX 119 bytes
I (5065) usb_rx: RX 183 bytes
I (5965) usb_rx: RX 42 bytes
I (6395) usb_rx: RX 119 bytes
I (9065) usb_rx: RX 183 bytes
I (17075) usb_rx: RX 183 bytes
I (18135) usb_rx: RX 42 bytes
I (18145) usb_tx: TX 42 bytes
I (18145) usb_rx: RX 74 bytes
I (18145) usb_tx: TX 58 bytes
I (18145) usb_rx: RX 74 bytes
I (18145) usb_tx: TX 58 bytes
I (18155) usb_rx: RX 54 bytes
I (18155) usb_rx: RX 536 bytes
I (18155) usb_rx: RX 54 bytes
4466   3 mongoose.c:12087:accept_conn   2 49 accepted 192.168.7.2:40546 -> 192.168.7.1:80
447a   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 88
447a   3 mongoose.c:12087:accept_conn   3 50 accepted 192.168.7.2:40552 -> 192.168.7.1:80
44a2   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
44c0   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
44de   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
44fc   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
451a   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
I (18375) usb_rx: RX 536 bytes
I (18375) usb_tx: TX 54 bytes
4538   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
4556   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
4574   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
4592   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11
45b0   3 mongoose.c:11937:read_conn     2 49 0:0:482 -2 err 11

[scaprile]

You are using lwIP, there's almost no Mongoose in there, there's nothing we can do

[imdahisaria]

Hi Scaprile. Thank you for the feedback. But is there any other way i could access the webserver via USB on esp32 ?

[scaprile]

Please see our documentation, and follow the guidelines in our tutorials.
https://mongoose.ws/documentation/tutorials/rp2040/pico-rndis-dashboard/
https://mongoose.ws/documentation/tutorials/stm32/all-make-baremetal-builtin-rndis/