无法通过arduino / ESP8266连接到ThingSpeak API

Question

我使用arduino和wifi盾牌将数据发布到ThingSpeak。我上周有这个工作，但现在我无法连接到ThingSpeak API来发布我的数据。相关功能是：

void sendData(String tsData) {
  ESP8266Client client;
  client.connect(thingSpeakAddress, 80);
  delay(1000);
  Serial.print("Attempting to send data...");
  if (client.connected())
  {
    client.print("POST /update HTTP/1.1\n");
    client.print("Host: api.thingspeak.com\n");
    client.print("Connection: close\n");
    client.print("X-THINGSPEAKAPIKEY: "+writeKey+"\n");
    client.print("Content-Type: application/x-www-form-urlencoded\n");
    client.print("Content-Length: ");
    client.print(tsData.length());
    client.print("\n\n");
    client.println(tsData);
    lastConnectionTime = millis();

    if (client.connected())
    {
      Serial.println("Connected to ThingSpeak!");
      Serial.println();
      Serial.print("Sent data: ");
      Serial.println(tsData);
      Serial.print("\n");
      failedCounter = 0;
    }
    else
    {
      failedCounter++;

      Serial.println("Connection to ThingSpeak failed");   
      Serial.println();
      Serial.print("Tried to send data: ");
      Serial.println(tsData);
      Serial.print("\n");
    }
  }
  else
  {
    failedCounter++;

    Serial.println("Connection to ThingSpeak Failed");   
    Serial.println();

    lastConnectionTime = millis(); 
  }

}

然而，我无法连接。每次我得到＆＃34;与ThingSpeak的连接失败。＆＃34;为什么我不能连接？有没有更好的方法来解决这个问题？