In case you have multiple APs with the same SSID/password and WiFi.begin(ssid, pwd) is called, ESP32 defaults to connect to THE FIRST AP FOUND matching ssid - according to:
https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/network/esp_wifi.html#_CPPv418wifi_scan_method_t
This can cause situations that ESP32 is trying to connect to AP which is far away from it (weak signal) even there is AP close to it, just as in my house - I have AP on channel 6 which is in the 1st floor (quite far from room where I do the programming) and AP on channel 13 in the same room I do the programming (which is in the 2nd floor) - result: ESP32 is trying to connect to the AP on channel 6 because it finds it first and never try the AP on channel 13 in the same room, result of this is very unreliable WiFi connection.
When scan_method is set to WIFI_ALL_CHANNEL_SCAN, ESP32 scans all channels and choose the nearest / strongest AP (matching the ssid of course) as expected - result is no connection problems at all.
Therefore I propose adding this parameter into WiFi.begin, connection problems as described above are quite confusing (especially for beginners), I can imagine that for example Schools there are usually using mutliple APs and this can cause intermittent connection problems without obvious reason.
See #3960 for more details of the problem and the solution. I only implemented what was proposed in this ticket, as it solves my problem, which was the same as in this ticket. Credits for the code going to @etrinh ;-)
This also is a more consistence behaviour compared to esp8266, where it also is possible to restart the wifiserver immediately on the same port.
Real DNS resolving timeout used by lwip library is 14[s] (7[s] for DNS1 + 7[s] for DNS2). Function WiFiGenericClass::hostByName() has timeout set to lower value (only 4[s]), so callback function may be called after this low timeout and it may overlappe stack memory used now by other function.
Fixes#3722
1. WiFiProv.ino sketch is added that allows arduino users to do provisioning via SoftAP or BLE. WiFi.beginProvision( ) API is designed for provisioning in Arduino.
2. In WiFiProv.h provisioning class is defined.
3. WiFiProv.cpp contains implementation for provisioning class.
4. README.md file is added which contains detail information for working.
* std::shared_ptr Memory Leak
clientSocketHande and _rxBuffer are std::shared_ptr, the stop() call was not correctly releasing them and the operator= had similar problems fix for #3679
* operator= second attempt
* operator= third time
WiFiClient.connected() was hanging thinking there was still a connection when the remote had already closed. The one-liner in this patch addresses recv() returning 0 and errno==128. I couldn't find the corresponding errno for 128 but its caught by the case statement which includes EPIPE, ENOTCONN, ECONNRESET and ECONNABORTED so I assume its one of those. Broken pipe maybe?
```c
[D][WiFiClient.cpp:511] connected(): Disconnected: RES: 0, ERR: 128
```
EDIT: added comment to reflect that recv() can set errno when it returns 0.
fixed the connected() function so that it only checks errno if recv returns a value of -1.
"in the even of an error, errno is set to indicate the error" --manpage
This fixes the ESP32 Webserver when dealing with a modern webserver with a slow SD card.
This event name was missing in the list:
d5e2bb12ca/tools/sdk/include/esp32/esp_event_legacy.h (L43)
E.g., it was giving
[D][WiFiGeneric.cpp:337] _eventCallback(): Event: 24 - ETH_GOT_IP
When it should have been
[D][WiFiGeneric.cpp:337] _eventCallback(): Event: 24 - ETH_DISCONNECTED
* Added timeout to WiFiScan class to prevent haning at stucking at WIFI_SCAN_RUNNING when scan fails internally
* fixed tabs and returns, connected scanTimeout to max_scan_per_channel timeout
* Corrected tabs two
* Added static vars scanTimeout und scanStarted to WiFiScan.h protected section
* Fixed missing ; in line 64
* Add generic IP calculations
Add:
calculateNetworkID(IPAddress ip, IPAddress subnet) => Calculate the network id using the ip and subnet (e.g. 192.168.0.0)
calculateBroadcast(IPAddress ip, IPAddress subnet) => Calculate the broadcast ip using the ip and subnet (e.g. 192.168.0.255)
calculateSubnetCIDR(IPAddress subnetMask) => Calculate the subnet CIDR using the subnet (e.g. 24)
Add:
broadcastIP() => Retrieve the network id (e.g. 192.168.0.0)
networkID() => Retrieve the broadcast IP (e.g. 192.168.0.255)
subnetCIDR() => Retrieve the subnet CIDR (e.g. 24)
Add:
broadcastIP() => Retrieve the network id (e.g. 192.168.0.0)
networkID() => Retrieve the broadcast IP (e.g. 192.168.0.255)
subnetCIDR() => Retrieve the subnet CIDR (e.g. 24)
Add:
softAPBroadcastIP() => Retrieve the network id (e.g. 192.168.0.0)
softAPNetwrokID() => Retrieve the broadcast IP (e.g. 192.168.0.255)
softAPSubnetCIDR() => Retrieve the subnet CIDR (e.g. 24)
* add opportunity for more than one retry to _uploadReadByte
* an alternative timeout-based method to making _uploadReadByte more resilient
* move timing variables in the correct scope
* implement and use client.getTimeout instead of hard-coded timeout in _uploadReadByte
* add missing return
* some refactoring to address respecting the timeout in a potentially deadlocked connection
* fix spelling in comment
* address review comments; move impl to cpp file for getTimeout, and remove local variable for currentMillis
* remove redundant cast
* need to check for timeout outside the inner while as well
* update WebUpdate example to print something in unexpected callback condition
* update log_e messages per review comments
Currently WiFiClient::write is unable to send messages over 25Kb, because of the hard-coded retry limit of 10, that is getting decremented on every successful send. Since we cannot send more than 2*MTU bytes in one go, and have only 10 retries, write() is limited to approximately 25Kb. Technically it is not a bug, as it correctly returns the number of sent bytes and the caller can set up futher retries. But not all libs are aware of this behavior, for example, WebServer is not.
I suggest improving current behavior by resetting retry counter every time we had a successful write, so the limit of 10 retries will apply to Failed writes only, and will not apply to Successful writes. This will allow to write() blobs of arbitrary sizes.
