IP地址用char数组方式保存

如果你想将IP地址以`char`数组的方式保存，可以使用`IPAddress`类的`toString()`函数将其转换为字符串，然后使用`strcpy()`函数将字符串复制到`char`数组中。以下是一个示例代码：

#include <Preferences.h>

// 定义一个结构体来存储参数
struct WiFiSettings {
  char ssid[32];
  char password[64];
  char ip[16];
  char gateway[16];
  char subnet[16];
  uint16_t localPort;
  char tcpServerIP[16];
  uint16_t tcpServerPort;
};

// 创建Preferences实例
Preferences preferences;

void setup() {
  // 打开Preferences存储空间，并指定名称和命名空间
  preferences.begin("wifi_settings", false);

  // 读取参数值
  WiFiSettings wifiSettings;
  preferences.getBytes("wifi_settings", &wifiSettings, sizeof(wifiSettings));

  // 输出参数值到串口
  Serial.begin(9600);
  Serial.println("WiFi Settings:");
  Serial.print("SSID: ");
  Serial.println(wifiSettings.ssid);
  Serial.print("Password: ");
  Serial.println(wifiSettings.password);
  Serial.print("IP Address: ");
  Serial.println(wifiSettings.ip);
  Serial.print("Gateway: ");
  Serial.println(wifiSettings.gateway);
  Serial.print("Subnet Mask: ");
  Serial.println(wifiSettings.subnet);
  Serial.print("Local Port: ");
  Serial.println(wifiSettings.localPort);
  Serial.print("TCP Server IP: ");
  Serial.println(wifiSettings.tcpServerIP);
  Serial.print("TCP Server Port: ");
  Serial.println(wifiSettings.tcpServerPort);
}

void loop() {
  // ...
}

void saveWiFiSettings() {
  // 存储参数值
  WiFiSettings wifiSettings;
  strcpy(wifiSettings.ssid, "my_ssid");
  strcpy(wifiSettings.password, "my_password");
  IPAddress ip(192, 168, 1, 100);
  strcpy(wifiSettings.ip, ip.toString().c_str()); // 将IP地址转换为字符串并复制到char数组中
  IPAddress gateway(192, 168, 1, 1);
  strcpy(wifiSettings.gateway, gateway.toString().c_str()); // 将网关地址转换为字符串并复制到char数组中
  IPAddress subnet(255, 255, 255, 0);
  strcpy(wifiSettings.subnet, subnet.toString().c_str()); // 将子网掩码转换为字符串并复制到char数组中
  wifiSettings.localPort = 1234;
  IPAddress tcpServerIP(192, 168, 1, 200);
  strcpy(wifiSettings.tcpServerIP, tcpServerIP.toString().c_str()); // 将TCP服务器IP地址转换为字符串并复制到char数组中
  wifiSettings.tcpServerPort = 5678;
  preferences.putBytes("wifi_settings", &wifiSettings, sizeof(wifiSettings));
}

在上面的示例代码中，我们在`saveWiFiSettings()`函数中将IP地址转换为字符串，然后使用`strcpy()`函数将其复制到`char`数组中。注意，在调用`toString()`函数时，我们需要将其返回值转换为C风格的字符串，即使用`c_str()`函数。