This is needed since when the content-length header is not sent the clients will
wait for data anyways. Sending a content length of zero will tell the client not
to expect any content and it will close the connection immediately.
esp_iot_sdk_v1.5.1_16_01_08 Release Note
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Resolved Issues (Bugs listed below apply to Bug Bounty Program):
1.espconn_abort may cause system crash.
Optimization:
1.Optimize the data receiving process under TCP connection.
2.Optimize low MAC and increase stability of the software.
3.Optimize watchdog feeding process.
4.Optimize softAP working mode so that some stations can be easily connected.
5.Optimize station working mode, enabling connection even when the SSID of the AP has changed.
6.Optimize station working mode, and increase router’s compatibility during the connection process.
7.Optimize SSL shakehand.
8.Optimize espconn internal timer.
9.Optimize UDP transmission.
10.Improve the flash writing process.
11.Strenthen WPA2 security protocols.
12.Improve data sending ability.
13.Straighten the control capability of GPIO16 under light sleep mode.
14.boot.bin is upgrade to version 1.5, resolving boot failure when firmware is upgraded over the air (OTA).
AT release note：
1.Optimize the process of establishing TCP server via AT command.
2.Optimize UART-WiFi transparent transmission mode via AT command.
Please be noted that with the release of NONOS SDK Version 1.5.0 (ESP8266_NONOS_SDK_V1.5.0), the space that AT commands occupies has increased to more than 4Mbit. Therefore, flash with 512Kbit capacity is no longer supported. Please choose flash with at least 8Mbit capacity.
Please be noted that firmware upgrade over-the-air process is changed a bit. We will upgrade the latest firmware to Espressif Cloud server only after it has been tested and the overall performance is guaranteed. Users may not be able to download firmware encapsulated in ESP8266_NONOS_SDK_V1.5.0 and other more advanced versions.
