Add BLE stream classes.

Co-authored-by: doudar <17362216+doudar@users.noreply.github.com>

examples/NimBLE_Stream_Client/CMakeLists.txt

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+# The following lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.5)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(NimBLE_Stream_Client)

examples/NimBLE_Stream_Client/README.md

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+# NimBLE Stream Client Example
+
+This example demonstrates how to use the `NimBLEStreamClient` class to connect to a BLE GATT server and communicate using the familiar Arduino Stream interface.
+
+## Features
+
+- Uses Arduino Stream interface (print, println, read, available, etc.)
+- Automatic server discovery and connection
+- Bidirectional communication
+- Buffered TX/RX using ring buffers
+- Automatic reconnection on disconnect
+- Similar usage to Serial communication
+
+## How it Works
+
+1. Scans for BLE devices advertising the target service UUID
+2. Connects to the server and discovers the stream characteristic
+3. Initializes `NimBLEStreamClient` with the remote characteristic
+4. Subscribes to notifications to receive data in the RX buffer
+5. Uses familiar Stream methods like `print()`, `println()`, `read()`, and `available()`
+
+## Usage
+
+1. Build and flash the NimBLE_Stream_Server example to one ESP32 using ESP-IDF (`idf.py build flash monitor`)
+2. Build and flash this client example to another ESP32 using ESP-IDF
+3. The client will automatically:
+   - Scan for the server
+   - Connect when found
+   - Set up the stream interface
+   - Begin bidirectional communication
+4. Open `idf.py monitor` on each board to observe stream traffic
+
+## Service UUIDs
+
+Must match the server:
+- Service: `6E400001-B5A3-F393-E0A9-E50E24DCCA9E`
+- Characteristic: `6E400002-B5A3-F393-E0A9-E50E24DCCA9E`
+
+## Monitor Output
+
+The example displays:
+- Server discovery progress
+- Connection status
+- All data received from the server
+- Confirmation of data sent to the server
+
+## Testing
+
+Run with NimBLE_Stream_Server to see bidirectional communication:
+- Server sends periodic status messages
+- Client sends periodic uptime messages
+- Both echo data received from each other
+- You can send data from either `idf.py monitor` session

examples/NimBLE_Stream_Client/main/CMakeLists.txt

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+set(COMPONENT_SRCS "main.cpp")
+set(COMPONENT_ADD_INCLUDEDIRS ".")
+
+register_component()

examples/NimBLE_Stream_Client/main/main.cpp

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+/**
+ *  NimBLE_Stream_Client Example:
+ *
+ *  Demonstrates using NimBLEStreamClient to connect to a BLE GATT server
+ *  and communicate using the Stream-like interface.
+ *
+ *  This example connects to the NimBLE_Stream_Server example.
+ */
+
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "esp_timer.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+
+#include <NimBLEDevice.h>
+
+// Service and Characteristic UUIDs (must match the server)
+#define SERVICE_UUID        "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
+#define CHARACTERISTIC_UUID "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
+
+// Create the stream client instance
+NimBLEStreamClient bleStream;
+
+struct RxOverflowStats {
+    uint32_t droppedOld{0};
+    uint32_t droppedNew{0};
+};
+
+RxOverflowStats g_rxOverflowStats;
+uint32_t        scanTime = 5000; // Scan duration in milliseconds
+
+NimBLEStream::RxOverflowAction onRxOverflow(const uint8_t* data, size_t len, void* userArg) {
+    auto* stats = static_cast<RxOverflowStats*>(userArg);
+    if (stats) {
+        stats->droppedOld++;
+    }
+
+    // For status/telemetry streams, prioritize newest packets.
+    (void)data;
+    (void)len;
+    return NimBLEStream::DROP_OLDER_DATA;
+}
+
+static uint64_t millis() {
+    return esp_timer_get_time() / 1000ULL;
+}
+
+// Connection state variables
+static bool                          doConnect     = false;
+static bool                          connected     = false;
+static const NimBLEAdvertisedDevice* pServerDevice = nullptr;
+static NimBLEClient*                 pClient       = nullptr;
+
+/** Scan callbacks to find the server */
+class ScanCallbacks : public NimBLEScanCallbacks {
+    void onResult(const NimBLEAdvertisedDevice* advertisedDevice) override {
+        printf("Advertised Device: %s\n", advertisedDevice->toString().c_str());
+
+        // Check if this device advertises our service.
+        if (advertisedDevice->isAdvertisingService(NimBLEUUID(SERVICE_UUID))) {
+            printf("Found our stream server!\n");
+            pServerDevice = advertisedDevice;
+            NimBLEDevice::getScan()->stop();
+            doConnect = true;
+        }
+    }
+
+    void onScanEnd(const NimBLEScanResults& results, int reason) override {
+        (void)results;
+        (void)reason;
+        printf("Scan ended\n");
+        if (!doConnect && !connected) {
+            printf("Server not found, restarting scan...\n");
+            NimBLEDevice::getScan()->start(scanTime, false, true);
+        }
+    }
+} scanCallbacks;
+
+/** Client callbacks for connection/disconnection events */
+class ClientCallbacks : public NimBLEClientCallbacks {
+    void onConnect(NimBLEClient* pClient) override {
+        printf("Connected to server\n");
+        // Update connection parameters for better throughput.
+        pClient->updateConnParams(12, 24, 0, 200);
+    }
+
+    void onDisconnect(NimBLEClient* pClient, int reason) override {
+        (void)pClient;
+        printf("Disconnected from server, reason: %d\n", reason);
+        connected = false;
+        bleStream.end();
+
+        // Restart scanning.
+        printf("Restarting scan...\n");
+        NimBLEDevice::getScan()->start(scanTime, false, true);
+    }
+} clientCallbacks;
+
+/** Connect to the BLE Server and set up the stream */
+bool connectToServer() {
+    printf("Connecting to: %s\n", pServerDevice->getAddress().toString().c_str());
+
+    // Create or reuse a client.
+    pClient = NimBLEDevice::getClientByPeerAddress(pServerDevice->getAddress());
+    if (!pClient) {
+        pClient = NimBLEDevice::createClient();
+        if (!pClient) {
+            printf("Failed to create client\n");
+            return false;
+        }
+        pClient->setClientCallbacks(&clientCallbacks, false);
+        pClient->setConnectionParams(12, 24, 0, 200);
+        pClient->setConnectTimeout(5000);
+    }
+
+    // Connect to the remote BLE Server.
+    if (!pClient->connect(pServerDevice)) {
+        printf("Failed to connect to server\n");
+        return false;
+    }
+
+    printf("Connected! Discovering services...\n");
+
+    // Get the service and characteristic.
+    NimBLERemoteService* pRemoteService = pClient->getService(SERVICE_UUID);
+    if (!pRemoteService) {
+        printf("Failed to find our service UUID\n");
+        pClient->disconnect();
+        return false;
+    }
+    printf("Found the stream service\n");
+
+    NimBLERemoteCharacteristic* pRemoteCharacteristic = pRemoteService->getCharacteristic(CHARACTERISTIC_UUID);
+    if (!pRemoteCharacteristic) {
+        printf("Failed to find our characteristic UUID\n");
+        pClient->disconnect();
+        return false;
+    }
+    printf("Found the stream characteristic\n");
+
+    // subscribeNotify=true means notifications are stored in the RX buffer.
+    if (!bleStream.begin(pRemoteCharacteristic, true)) {
+        printf("Failed to initialize BLE stream!\n");
+        pClient->disconnect();
+        return false;
+    }
+
+    bleStream.setRxOverflowCallback(onRxOverflow, &g_rxOverflowStats);
+
+    printf("BLE Stream initialized successfully!\n");
+    connected = true;
+    return true;
+}
+
+extern "C" void app_main(void) {
+    printf("Starting NimBLE Stream Client\n");
+
+    /** Initialize NimBLE */
+    NimBLEDevice::init("NimBLE-StreamClient");
+
+    // Create the BLE scan instance and set callbacks.
+    NimBLEScan* pScan = NimBLEDevice::getScan();
+    pScan->setScanCallbacks(&scanCallbacks, false);
+    pScan->setActiveScan(true);
+
+    // Start scanning for the server.
+    printf("Scanning for BLE Stream Server...\n");
+    pScan->start(scanTime, false, true);
+
+    uint32_t lastDroppedOld = 0;
+    uint32_t lastDroppedNew = 0;
+    uint64_t lastSend       = 0;
+
+    for (;;) {
+        if (g_rxOverflowStats.droppedOld != lastDroppedOld || g_rxOverflowStats.droppedNew != lastDroppedNew) {
+            lastDroppedOld = g_rxOverflowStats.droppedOld;
+            lastDroppedNew = g_rxOverflowStats.droppedNew;
+            printf("RX overflow handled (drop-old=%" PRIu32 ", drop-new=%" PRIu32 ")\n", lastDroppedOld, lastDroppedNew);
+        }
+
+        // If we found a server, try to connect.
+        if (doConnect) {
+            doConnect = false;
+            if (connectToServer()) {
+                printf("Stream ready for communication!\n");
+            } else {
+                printf("Failed to connect to server, restarting scan...\n");
+                pServerDevice = nullptr;
+                NimBLEDevice::getScan()->start(scanTime, false, true);
+            }
+        }
+
+        // If connected, demonstrate stream communication.
+        if (connected && bleStream) {
+            if (bleStream.available()) {
+                printf("Received from server: ");
+                while (bleStream.available()) {
+                    char c = bleStream.read();
+                    putchar(c);
+                }
+                printf("\n");
+            }
+
+            uint64_t now = millis();
+            if (now - lastSend > 5000) {
+                lastSend = now;
+                bleStream.printf("Hello from client! Uptime: %" PRIu64 " seconds\n", now / 1000);
+                printf("Sent data to server via BLE stream\n");
+            }
+        }
+
+        vTaskDelay(pdMS_TO_TICKS(10));
+    }
+}

examples/NimBLE_Stream_Client/sdkconfig.defaults

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+# Override some defaults so BT stack is enabled
+# in this example
+
+#
+# BT config
+#
+CONFIG_BT_ENABLED=y
+CONFIG_BTDM_CTRL_MODE_BLE_ONLY=y
+CONFIG_BTDM_CTRL_MODE_BR_EDR_ONLY=n
+CONFIG_BTDM_CTRL_MODE_BTDM=n
+CONFIG_BT_BLUEDROID_ENABLED=n
+CONFIG_BT_NIMBLE_ENABLED=y