Allow definition of custom network interfaces (#921)

* Allow definition of custom network interfaces

* Create network client interface class

* Change to PIMPL approach

* Add example for custom network clients

Why:

- Show users how to use multiple network interfaces

This change addresses the need by:

- Adding an example PIO project to use Wi-Fi and GSM/LTE

* Add WebSockets prefix to normal and secure client

Why:

- Avoid name collision
- Fix broken reconnect change

This change addresses the need by:

- Adding WebSockets prefix to all custom clients
- Marking custom client as secure in clientDisconnect()
  - Remove broken fix for reconnecting

examples/esp32_pio/CustomNetworkClient/src/main.cpp

@@ -0,0 +1,126 @@
+/*
+ * main.cpp
+ *
+ *  Created on: 15.06.2024
+ *
+ */
+
+#include <Arduino.h>
+#include <WebSocketsClient.h>
+#include <WiFiMulti.h>
+
+#include "network_client_impl.h"
+
+WiFiMulti wifiMulti;
+WebSocketsClient webSocket;
+
+#define USE_SERIAL Serial
+
+void setClock() {
+  configTime(0, 0, "pool.ntp.org", "time.nist.gov");
+
+  USE_SERIAL.print(F("Waiting for NTP time sync: "));
+  time_t nowSecs = time(nullptr);
+  while (nowSecs < 8 * 3600 * 2) {
+    delay(500);
+    USE_SERIAL.print(F("."));
+    yield();
+    nowSecs = time(nullptr);
+  }
+
+  USE_SERIAL.println();
+  struct tm timeinfo;
+  gmtime_r(&nowSecs, &timeinfo);
+  USE_SERIAL.print(F("Current time: "));
+  USE_SERIAL.print(asctime(&timeinfo));
+}
+
+void hexdump(const void *mem, uint32_t len, uint8_t cols = 16) {
+  const uint8_t *src = (const uint8_t *)mem;
+  USE_SERIAL.printf("\n[HEXDUMP] Address: 0x%08X len: 0x%X (%d)",
+                    (ptrdiff_t)src, len, len);
+  for (uint32_t i = 0; i < len; i++) {
+    if (i % cols == 0) {
+      USE_SERIAL.printf("\n[0x%08X] 0x%08X: ", (ptrdiff_t)src, i);
+    }
+    USE_SERIAL.printf("%02X ", *src);
+    src++;
+  }
+  USE_SERIAL.printf("\n");
+}
+
+void webSocketEvent(WStype_t type, uint8_t *payload, size_t length) {
+  switch (type) {
+    case WStype_DISCONNECTED:
+      USE_SERIAL.printf("[WSc] Disconnected!\n");
+      break;
+    case WStype_CONNECTED:
+      USE_SERIAL.printf("[WSc] Connected to url: %s\n", payload);
+
+      // send message to server when Connected
+      webSocket.sendTXT("Connected");
+      break;
+    case WStype_TEXT:
+      USE_SERIAL.printf("[WSc] get text: %s\n", payload);
+
+      // send message to server
+      // webSocket.sendTXT("message here");
+      break;
+    case WStype_BIN:
+      USE_SERIAL.printf("[WSc] get binary length: %u\n", length);
+      hexdump(payload, length);
+
+      // send data to server
+      // webSocket.sendBIN(payload, length);
+      break;
+    case WStype_ERROR:
+    case WStype_FRAGMENT_TEXT_START:
+    case WStype_FRAGMENT_BIN_START:
+    case WStype_FRAGMENT:
+    case WStype_FRAGMENT_FIN:
+      break;
+  }
+}
+
+void setup() {
+  USE_SERIAL.begin(115200);
+
+  USE_SERIAL.setDebugOutput(true);
+
+  USE_SERIAL.println();
+  USE_SERIAL.println();
+  USE_SERIAL.println();
+
+  for (uint8_t t = 4; t > 0; t--) {
+    USE_SERIAL.printf("[SETUP] BOOT WAIT %d...\n", t);
+    USE_SERIAL.flush();
+    delay(1000);
+  }
+
+  wifiMulti.addAP("Berge", "BlauerHimmel!");
+
+  // WiFi.disconnect();
+  while (wifiMulti.run() != WL_CONNECTED) {
+    delay(100);
+  }
+
+  // Call to enable WiFi interface to be used by the webSocketClient
+  WebSocketsNetworkClient::Impl::enableWifi();
+
+  setClock();
+
+  // server address, port and URL. This server can be flakey.
+  // Expected response: Request served by 0123456789abcdef
+  webSocket.beginSSL("echo.websocket.org", 443, "/");
+
+  // event handler
+  webSocket.onEvent(webSocketEvent);
+
+  // use HTTP Basic Authorization this is optional enable if needed
+  // webSocket.setAuthorization("user", "Password");
+
+  // try ever 5000 again if connection has failed
+  webSocket.setReconnectInterval(5000);
+}
+
+void loop() { webSocket.loop(); }