如何在POST标注中设置正文？

我有一个连接到 esp8266 的湿度和温度传感器，现在我想将数据发送到云端。我无法上班的是 POST 电话。下面的 POST 请求在 Auth() 函数中返回一条错误消息，告诉我正文没有按预期发送。
我让 api 在 Postman 中正常工作，所以我确定凭据没问题等等。
有人有关于如何执行 POST 请求并正确发送此正文的示例吗？我重新搜索了文档，但只能找到一个 GET 示例……
在此先感谢！  
代码：全选#include
#include
#include

#include \"credentials.h\"

#include
#include

#define DHTPIN 2
#define DHTTYPE    DHT21

const char* host = \"login.salesforce.com\";
const int httpsPort = 443;

// SHA1 fingerprint of the certificate
const char fingerprint[] PROGMEM = \"0B 33 19 AC 6D 9E C1 5F 08 AB 93 17 2A FE F9 E0 90 69 C7 9A\"; //login.salesforce.com

DHT_Unified dht(DHTPIN, DHTTYPE);

int delayMS = 3000;
String requestBody;

void setup() {
  Serial.begin(115200); // Initialize device.
  dht.begin(); // Initialize sensors
  Serial.println();
  Serial.printf(\"Connecting to %s\", ssid);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password); // Connect to Wifi
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(\".\");
  }
  Serial.println();
  Serial.println(\"WiFi connected\");
  Serial.print(\"IP address: \");
  Serial.println(WiFi.localIP());
  auth();
}

void loop() {
  // Get temperature event and print its value.
  sensors_event_t event;
  dht.temperature().getEvent(&event);
  if (isnan(event.temperature)) {
    Serial.println(F(\"Error reading temperature!\"));
  }
  else {
    Serial.print(\"Temperature: \");
    Serial.print(event.temperature);
    Serial.println(\"°C\");
  }
  // Get humidity event and print its value.
  dht.humidity().getEvent(&event);
  if (isnan(event.relative_humidity)) {
    Serial.println(F(\"Error reading humidity!\"));
  }
  else {
    Serial.print(F(\"Humidity: \"));
    Serial.print(event.relative_humidity);
    Serial.println(F(\"%\"));
  }
  // Delay between measurements.
  delay(delayMS);
}

void auth() {
  WiFiClientSecure client;
  requestBody = \"grant_type=password&client_id=\" + consumerKey + \"&client_secret=\" + consumerSecret + \"&username=\" + userUsername + \"&password=\" + userPassword;
   
  Serial.printf(\"connecting to %s using fingerprint %s\\n\", host, fingerprint);

  client.setFingerprint(fingerprint);
  
  if (!client.connect(host, httpsPort)) {
    Serial.println(\"connection failed\");
    return;
  } else {
    Serial.println(\"Connected\");
  }

  String url = \"/services/oauth2/token\";
  Serial.print(\"requesting URL: \");
  Serial.println(url);

  client.print(String(\"POST \") + url + \" HTTP/1.1\\r\\n\" +
               \"Host: \" + host + \"\\r\\n\" +
               \"Content-Type: application/x-www-form-urlencoded\\r\\n\" +
               requestBody + \"\\r\\n\\r\\n\");

  Serial.print(String(\"POST \") + url + \" HTTP/1.1\\r\\n\" +
               \"Host: \" + host + \"\\r\\n\" +
               \"Content-Type: application/x-www-form-urlencoded\\r\\n\" +
               requestBody + \"\\r\\n\\r\\n\");

  Serial.println(\"request sent\");
  while (client.connected()) {
    String line = client.readStringUntil(\'\\n\');
    if (line == \"\\r\") {
      Serial.println(\"headers received\");
      break;
    }
  }
  String line = client.readString();
  if (line.startsWith(\"{\\\"state\\\":\\\"success\\\"\")) {
    Serial.println(\"Authentication successfull!\");
  } else {
    Serial.println(\"Authentication failed\");
  }
  Serial.println(\"reply was:\");
  Serial.println(\"==========\");
  Serial.println(line);
  Serial.println(\"==========\");
  Serial.println(\"closing connection\");
}


我真的很感激任何帮助！