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.

* WiFiClient.cpp - Fix connect() behavior

* lwip_connect_r() : check return code

* 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.

* Add timeout to WiFiClient.connect()

* Changed default handling

Fix error in PR #2048: if ::available() is called before ::connect() _rxBuffer is not initialised (#2155)

#2147 available() shouldn't return 0 after disconnect if there is still data in the buffer. Otherwise, how would we know it was there? (#2148)

* Use right function for BSSID

* removing log

* Clean warnings when all warning enabled

Not used variables / functions due to debug log

Dual define with different values :
cores\esp32/binary.h
#define B110 6
#define B1000000 64

tools/sdk/include/newlib/sys/termios.h
#define B110        3
#define B1000000   23

Local variable returned in WiFiclient Secure

* change due to deprecated function

* Update with proper variable and label

* Update esp32-hal-i2c.c

* Apply changes requested

* Fix warnings due to #define conflict thanks @atanisoft

* Pass client parameter into two new begin() functions. Set other begin() functions deprecated. Updated library version to 1.2

* Added working HTTPS example on a public url with a certificate

* Remove two unnecessary tests in ::disconnect()

* Add a scoping block to BasicHttpsClient.ino to assure HTTPClient is destroyed before WiFiClientSecure

* Added check to handle mixup of old and present api properly

* Correct HTTPClient::setTimeout() to convert milliseconds to seconds. Correct WiFiClient::setTimeout() to call Stream::setTimeout() with seconds converted back to milliseconds. Remove inproper checks for _insecure.

* Added small comment because it looked like the Travis build did not finish

* fix sdmmc config

* Fix warnings in EEPROM

from @Curclamas

* remove leftover TAG in EEPROM

* Initial add of @stickbreaker i2c

* Add log_n

* fix warnings when log is off

* i2c code clean up and reorganization

* add flags to interrupt allocator

* fix sdmmc config

* Fix warnings in EEPROM

from @Curclamas

* remove leftover TAG in EEPROM

* fix errors with latest IDF

* fix debug optimization (#1365)

incorrect optimization for debugging tick markers.

* Fix some missing BT header

* Change BTSerial log calls

* Update BLE lib

* Arduino-ESP32 release management scripted (#1515)

* Calculate an absolute path for a custom partitions table (#1452)

* * Arduino-ESP32 release management scripted
(ready-to-merge)

* * secure env for espressif/arduino-esp32

* * build tests enabled
* gitter webhook enabled

* * gitter room link fixed
* better comment

* * filepaths fixed

* BT Serial adjustments

* * don't run sketch builds & tests for tagged builds

* Return false from WiFi.hostByName() if hostname is not resolved

* Free BT Memory when BT is not used

* WIFI_MODE_NULL is not supported anymore

* Select some key examples to build with PlatformIO to save some time

* Update BLE lib

* Fixed BLE lib

* Major WiFi overhaul

- auto reconnect on connection loss now works
- moved to event groups
- some code clean up and procedure optimizations
- new methods to get a more elaborate system ststus

* Add cmake tests to travis

* Add initial AsyncUDP

* Add NetBIOS lib and fix CMake includes

* Add Initial WebServer

* Fix WebServer and examples

* travis not quiting on build fail

* Try different travis build

* Update IDF to aaf1239

* Fix WPS Example

* fix script permission and add some fail tests to sketch builder

* Add missing space in WiFiClient::write(Stream &stream)

send() can return a value > 0 but less than size indicating it was able to accept some of the data in buffer. The caller must try again after updating the buffer pointer and size remaining.

Required for WebServer and/or DNSServer libraries

Implement methods from ESP8266WiFiClient but use sockets API.

Thanks @miomir1981

* Add setNoDelay and getNoDelay to WiFiServer class

* Remote TCP disconnect not detected

Fixes: https://github.com/espressif/arduino-esp32/issues/263

fixes: https://github.com/espressif/arduino-esp32/issues/119

* Rework WiFiClient

Rework WiFiClient to correct error where making a copy of a WiFiClient object resulted in the socket being closed prematurely.

Added loop and select to write to handle/prevent EAGAIN errors.

* Rework WiFiClient to use shared_ptr

Rework changes to utilize shared_ptr rather than manually maintaining reference count. 

Revert changes to write

* Incorporate comments from review

Move WiFiClientSocketHandle and fd() into WiFiClient.cpp

The send call may return EAGAIN. This indicates a recoverable error and a retry should be attempted. The current implementation treats this as a fatal error. Further, the current implementation strips the error code, setting it to 0, which prevents the caller from handling it directly. 
This change utilizes select to verify the socket is available prior to calling send and will retry on an EAGAIN condition.

need close(sockfd) before sockfd = -1, "_connected = false and close socket" means stop() function. (#73)