Use asynchronous UDP library to get non blocking time update

[gmag11]

Now that I have the control of NTP sync procedure, it would be a very nice feature to add non blocking NTP request. This is possible by using ESPAsyncUDP library.

This have a side effect. Using this library would make next versions of NTPClientLib compatible only with ESP8266 and ESP32, as there is no equivalent library for MKR1000 and ArduinoWiFi.

Please add your thoughts and ideas in this issue.

[gmag11]

Initial support of asynchronous UDP communication is ready in AsyncUDP branch. There can be many bugs but it is compiling and working in my local setup.
There is no timeout processing yet, so issues may happen in case of no response from server.
This version is and will be only compatible with ESP32 and ESP8266 so if you are working with Arduino boards keep version 2.5.0.
Please test it and comment here. @AlbertWeterings @xoseperez

[gmag11]

Notice that for some time, I've moved NTPClientLib.h and .cpp to ESP8266 example folder. I need it so that Visual Studio Intellisense works properly. Move them to src folder for testing if you prefer to.

[gmag11]

Timeout processing is working now, using Ticker library. I've chosen this lib better than timer interrupts because it is available both on ESP8266 and ESP32 Arduino framework.

[mcspr]

It should be noted that hostByName uses delay internaly, and that just blocks if there is any error.

NtpClient/examples/NTPClientESP8266/NTPClientLib.cpp

Line 193 in c2031dd

int error = WiFi.hostByName (getNtpServerName ().c_str (), timeServerIP);

For example, ESPAsyncTCP client code directly uses sdk dns resolution

What I am thinking about is maybe do the same? Instead of hostByName use dns_gethostbyname and allow the caller not wait for broken dns server. Internal resolver will then just call given NtpClient callback and client will either connect or just cache the ip.

Edit: Plus, I was running this since yesterday without any issues. Disabled dns server, wrong ntp server ip, wrong dns address - client recovered and is ok so far.

[gmag11]

Good point! I did not think about this. I'll do that. Thanx

[Misiu]

@gmag11 thank You for such an awesome library.
I'd like to know if Async version is working and is it released? The latest release is 2.5.1 and I'm not sure if it includes async code.
I'm using ESP8266, so I guess that this example should be my base code.

[gmag11]

Hi. No, it is not released in master branch. But you can use it by selecting AsyncUDP branch. https://github.com/gmag11/NtpClient/tree/AsyncUDP
Notice it may contain some bug. At least for me, it was working fine. DNS async resolution is still missing so it is better if you configure NTP server IP address instead of server name.
Please let me know your experience with it.

[Misiu]

@gmag11 I'll try that version today. Hopefully, I'll create something working :)
@mcspr maybe You can create PR with Your suggested change? This way we'll be one step closer to releasing this into the master branch.

[mcspr]

@Misiu i'll take a look at it again this week. plus fixing minor esp32 example errors, as code paths will be the same for both esp8266 and esp32.

By the way... sdk itself does provide sntp (and timelib analogue) support and arduino for both esp8266/32 expose it. have you tried it?
esp8266/arduino entrypoint for ntp config
esp8266/arduino usage example (exact same api for esp32) and imagine 'delay' is replaced with timestamp checker somewhere in loop

[Misiu]

@mcspr I never used the built-in sntp functions (I didn't know they existed till now 😄 )
For my next project, I need wifi, mqtt and sntp. I want all of those to connect async to not complicate my loop code. The best scenario (everything connects and never disconnects) is simple, but if something disconnects I want to reconnect as easy as possible.
Do you know if configTime has a callback? I want to get time at start and every hour I want to resync it. Without any callback it will be hard to know that sync failed.

[gmag11]

I used them in older versions. But it was a mess to mantain different code for each platform. By that time esp32 did not include same sntp functions in its sdk, so I decided to get that code out of this library.

[Misiu]

@gmag11 so right now I could use configTime from SDK. What about callbacks, are there any available (ntp sync fsuccess, ntp sync fail)? I can't test it right now, but I found this example and this one, is it a good start?
I currently target ESP8266, so I don't mind if something is missing in ESP32 SDK :)

[mcspr]

(assuming recent esp8266/Arduino + lwip2 is used. my understanding is old sdk/lwip1.4 required manual sync because of some bugs)

Quick look at how sntp/time works there, because I was interested how it compared to ntpclient/timelib combo. Initial success is determined by checking if sntp_get_current_timestamp() returns >0, as examples show via time() usage. After that:
If sntp successfuly retrieves timestamp it will schedule next sync based on SNTP_UPDATE_DELAY
Which is set by arduino core to be 1 hour
sntp will relentlessy retry each server until it gets time
Core sets SNTP_RETRY_TIMEOUT and SNTP_RETRY_TIMEOUT_MAX (3 and 30 seconds respectively)

And it will autotrigger sync when network settings change, so i believe it is set-and-forget. No error state to check though, besides initial sync success.

edit in the example that @Misiu mentioned, there is cb when time is set:
https://github.com/esp8266/Arduino/blob/91519309d000c65c283c6721ae58d4bf708bf719/libraries/esp8266/examples/NTP-TZ-DST/NTP-TZ-DST.ino#L39-L49