multiple servers support

[mangooose]

Is it possible to connect to multiple servers? if yes what's the maximum number of connections?

[chegewara]

With this library its not possible, not yet.

[mangooose]

Any other alternatives that works with arduino?

[chegewara]

Nothing i know, but you can use esp-idf commands.

[mangooose]

How? should I just include the esp-idf headers?

[chegewara]

There is SimplBLE example, start with it. im guessing esp_bt.h header will be usable at begining.

I will try to find some time and add multi-connection support to this library, but its quite a lot code to write i think (server and client part, notify/indicate etc).

[mangooose]

Thanks a lot :)

[chegewara]

When im thinking about it i see first issue, each server that will be connected have list of services, characteristics and descriptors. The issue is that we need to enumerate each of them separately.

[mangooose]

What about this pull request?(the multiple client support part)

[chegewara]

Like i said, there is a lot things to consider and some code needs to be re-thinked and changed. This is just example:
https://github.com/nkolban/esp32-snippets/pull/541/files#diff-6b48b04d9f9202e7dc8114b588e968baR98

Now on each connection to server service table is cleared, but it wont work with multi-connecting. This needs to be moved into disconnect part. This is not considered in that pull request and many more very important things. I have to review whole code again and make some plan first.

[chegewara]

@mangooose I have some code ready, it was much simpler than i thought, but of course it requires some more tests in real life before can be used (i tested it with 2 esp32 servers and 1 esp32 client). Here is log:

D (28776) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (29089) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (29090) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (29091) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (29101) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (29123) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (29674) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (29675) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (29676) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (29686) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (29708) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (29822) BLEDevice: gattClientEventHandler [esp_gatt_if: 3] ... ESP_GATTC_NOTIFY_EVT
D (29823) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (29824) BLEUtils: [conn_id: 0, remote_bda: 30:ae:a4:43:a1:72, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (29834) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (29856) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (30259) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (30260) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (30261) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (30271) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (30293) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (30844) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (30845) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (30846) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (30856) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (30878) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (30917) BLEDevice: gattClientEventHandler [esp_gatt_if: 3] ... ESP_GATTC_NOTIFY_EVT
D (30918) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (30919) BLEUtils: [conn_id: 0, remote_bda: 30:ae:a4:43:a1:72, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (30929) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (30951) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (31429) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (31430) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (31431) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (31441) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (31463) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (31997) BLEDevice: gattClientEventHandler [esp_gatt_if: 3] ... ESP_GATTC_NOTIFY_EVT
D (31998) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (31999) BLEUtils: [conn_id: 0, remote_bda: 30:ae:a4:43:a1:72, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (32009) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (32031) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (32042) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (32050) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (32055) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (32065) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (32087) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (32599) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (32600) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (32601) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (32611) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (32633) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (33077) BLEDevice: gattClientEventHandler [esp_gatt_if: 3] ... ESP_GATTC_NOTIFY_EVT
D (33078) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (33079) BLEUtils: [conn_id: 0, remote_bda: 30:ae:a4:43:a1:72, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (33089) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (33111) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (33184) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (33185) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (33186) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (33196) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0
D (33218) SampleClient_Notify: Notify callback for characteristic 00002a2b-0000-1000-8000-00805f9b34fb of data length 1
D (33769) BLEDevice: gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_NOTIFY_EVT
D (33770) BLEUtils: GATT Event: ESP_GATTC_NOTIFY_EVT
D (33771) BLEUtils: [conn_id: 1, remote_bda: 30:ae:a4:3f:24:4e, handle: 42 0x2a, value_len: 1, is_notify: 1]
D (33781) BLERemoteCharacteristic: Invoking callback for notification on characteristic Characteristic: uuid: 00002a2b-0000-1000-8000-00805f9b34fb, handle: 42 0x2a, props: broadcast: 0, read: 1, write_nr: 0, write: 1, notify: 1, indicate: 1, auth: 0

Explanation:

• one server is sending notification every 500ms and one server is sending notification every 100ms,
• here is client app i am using for testing:

/**
 * Create a sample BLE client that connects to a BLE server and then waits for server generated
 * notifications and logs them when they arrive.
 */
#include <esp_log.h>
#include <string>
#include <sstream>
#include <sys/time.h>
#include "BLEDevice.h"

#include "BLEAdvertisedDevice.h"
#include "BLEClient.h"
#include "BLEScan.h"
#include "BLEUtils.h"
#include "Task.h"

#include "sdkconfig.h"

static const char* LOG_TAG = "SampleClient_Notify";

// See the following for generating UUIDs:
// https://www.uuidgenerator.net/

BLEScan *pBLEScan;
static uint16_t connID = 0;

static void notifyCallback(
	BLERemoteCharacteristic* pBLERemoteCharacteristic,
	uint8_t* pData,
	size_t length,
	bool isNotify) {
		ESP_LOGD(LOG_TAG, "Notify callback for characteristic %s of data length %d",
				pBLERemoteCharacteristic->getUUID().toString().c_str(), length);
}

/**
 * Become a BLE client to a remote BLE server.  We are passed in the address of the BLE server
 * as the input parameter when the task is created.
 */
class MyClient: public Task {
	void run(void* data) {
		BLEAddress* pAddress = (BLEAddress*)data;
		BLEClient*  pClient  = BLEDevice::createClient(connID++);

		// Connect to the remove BLE Server.
		pClient->connect(*pAddress);

		// Obtain a reference to the service we are after in the remote BLE server.
		BLERemoteService* pRemoteService = pClient->getService(BLEUUID((uint16_t)0x1805));
		if (pRemoteService == nullptr) {
			ESP_LOGD(LOG_TAG, "Failed to find our service UUID: %s", BLEUUID((uint16_t)0x1805).toString().c_str());
			return;
		}


		// Obtain a reference to the characteristic in the service of the remote BLE server.
		BLERemoteCharacteristic* pRemoteCharacteristic = pRemoteService->getCharacteristic(BLEUUID((uint16_t)0x2a2b));
		if (pRemoteCharacteristic == nullptr) {
			ESP_LOGD(LOG_TAG, "Failed to find our characteristic UUID: %s", BLEUUID((uint16_t)0x2a2b).toString().c_str());
			return;
		}

		// Read the value of the characteristic.
		// std::string value = pRemoteCharacteristic->readValue();
		// ESP_LOGD(LOG_TAG, "The characteristic value was: %s", value.c_str());

		pRemoteCharacteristic->registerForNotify(notifyCallback);

		ESP_LOGD(LOG_TAG, "%s", pClient->toString().c_str());
		ESP_LOGD(LOG_TAG, "-- End of task");

		pBLEScan->start(3);
	} // run
}; // MyClient


/**
 * Scan for BLE servers and find the first one that advertises the service we are looking for.
 */
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
	/**
	 * Called for each advertising BLE server.
	 */
	void onResult(BLEAdvertisedDevice advertisedDevice) {
		ESP_LOGD(LOG_TAG, "Advertised Device: %s", advertisedDevice.toString().c_str());

		if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(BLEUUID((uint16_t)0x1805))) {
			advertisedDevice.getScan()->stop();

			ESP_LOGD(LOG_TAG, "Found our device!  address: %s", advertisedDevice.getAddress().toString().c_str());
			MyClient* pMyClient = new MyClient();
			pMyClient->setStackSize(20000);
			pMyClient->start(new BLEAddress(*advertisedDevice.getAddress().getNative()));
		} // Found our server
	} // onResult
}; // MyAdvertisedDeviceCallbacks


/**
 * Perform the work of a sample BLE client.
 */
void SampleClient_Notify(void) {
	ESP_LOGD(LOG_TAG, "SampleClient_Notify starting");
	BLEDevice::init("esp32");
	pBLEScan = BLEDevice::getScan();
	pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
	pBLEScan->setActiveScan(true);
	pBLEScan->start(3);
} // SampleClient

I will push it to my github now and if will pass tests i will create PR, if you want to use it with arduino-ide then you need to prepare zip file or copy/paste modified files.

[mangooose]

@chegewara Thanks for your quick reply :) I will try it today and give you feedback

[chegewara]

But i have to warn you its not finished yet, but i have no tools/examples to perform full tests and see what is missing.

[mangooose]

@chegewara I just updated the files and made a quick sketch to test it and i'm still not able to connect to multiple servers. Here's my code:

    pClient1 = BLEDevice::createClient(0);
    pClient1->connect(*pServerAddress[0]);
    Serial.println("1 connected");
    BLERemoteCharacteristic* pRemoteCharacteristic1 =  pClient1->getService(ServiceUUID)->getCharacteristic(charUUID);

    pClient2 = BLEDevice::createClient(1);
    pClient2->connect(*pServerAddress[1]);
    Serial.println("2 connected");
    BLERemoteCharacteristic* pRemoteCharacteristic2 =  pClient2->getService(ServiceUUID)->getCharacteristic(charUUID);
    delay(1000);

    pRemoteCharacteristic1->writeValue((uint8_t*)x, 7, true);
    Serial.println("color1 changed");
    pRemoteCharacteristic2->writeValue((uint8_t*)x, 7, true);
    Serial.println("color2 changed");

last thing it shows is "2 connected"

[chegewara]

@mangooose This looks like code stuck somewhere on semaphore.

You can try and change this line:
if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(BLEUUID((uint16_t)0x1805))) {
with:
if (strcmp(advertisedDevice.getAddress().toString(), "aa:aa:aa:aa:aa:aa")) {
or something like that.

Try this with my previous example.

[mangooose]

Currently I don't have enough ESP32 to test with your example. On my example, I search for new BLE devices this a specific serviceUUID and then I try to connect with these devices. The first device can connect and can also change characteristics value. But when I connect to more than one device it can connect but hangs when I try to change the RemoteCharacteristic value.