server.available() according to reference. with example

[JAndrassy]

The reference for WiFi101 server.available() has

Gets a client that is connected to the server and has data available for reading.

which is same as for the Ethernet library and WiFiNINA library, and many other libraries implementing the Arduino networking API introduced by the Ethernet library.

But server.available() in WiFi101 library now returns a just connected client even if it doesn't have data available yet. (This is an interesting workaround for missing accept() function, but it is causing problems sometimes even with the examples of the WiFi101 library.)

This PR fixes available() and my other PR adds accept(), but the change of available() should be considered as breaking change, because sketch which expected server.available() to return new connected clients even without data, will break.

and the PR contains my example PagerServer (already accepted in Ethernet library) which concentrates on how server.available() and print-to-all-clients works.

[github-actions]

Memory usage change @ 7d8c54e

Board	flash	%	RAM for global variables	%
Intel:arc32:arduino_101	💚 -12 - 0	-0.01 - 0.0	N/A	N/A
arduino:avr:mega	💚 -44 - 0	-0.02 - 0.0	0 - 0	0.0 - 0.0
arduino:avr:uno	💚 -34 - 0	-0.11 - 0.0	0 - 0	0.0 - 0.0
arduino:sam:arduino_due_x_dbg	💚 -16 - 0	-0.0 - 0.0	N/A	N/A
arduino:samd:arduino_zero_edbg	💚 -8 - 0	-0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkr1000	💚 -8 - 0	-0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/AP_SimpleWebServer flash	%	examples/AP_SimpleWebServer RAM for global variables	%	examples/CheckWifi101FirmwareVersion flash	%	examples/CheckWifi101FirmwareVersion RAM for global variables	%	examples/ConnectNoEncryption flash	%	examples/ConnectNoEncryption RAM for global variables	%	examples/ConnectWithWEP flash	%	examples/ConnectWithWEP RAM for global variables	%	examples/ConnectWithWPA flash	%	examples/ConnectWithWPA RAM for global variables	%	examples/MDNS_WiFiWebServer flash	%	examples/MDNS_WiFiWebServer RAM for global variables	%	examples/Provisioning_WiFiWebServer flash	%	examples/Provisioning_WiFiWebServer RAM for global variables	%	examples/ScanNetworks flash	%	examples/ScanNetworks RAM for global variables	%	examples/ScanNetworksAdvanced flash	%	examples/ScanNetworksAdvanced RAM for global variables	%	examples/SimpleWebServerWiFi flash	%	examples/SimpleWebServerWiFi RAM for global variables	%	examples/WiFiChatServer flash	%	examples/WiFiChatServer RAM for global variables	%	examples/WiFiPing flash	%	examples/WiFiPing RAM for global variables	%	examples/WiFiSSLClient flash	%	examples/WiFiSSLClient RAM for global variables	%	examples/WiFiUdpNtpClient flash	%	examples/WiFiUdpNtpClient RAM for global variables	%	examples/WiFiUdpSendReceiveString flash	%	examples/WiFiUdpSendReceiveString RAM for global variables	%	examples/WiFiWebClient flash	%	examples/WiFiWebClient RAM for global variables	%	examples/WiFiWebClientRepeating flash	%	examples/WiFiWebClientRepeating RAM for global variables	%	examples/WiFiWebServer flash	%	examples/WiFiWebServer RAM for global variables	%	examples/FirmwareUpdater flash	%	examples/FirmwareUpdater RAM for global variables	%
Intel:arc32:arduino_101	-12	-0.01	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	-12	-0.01	N/A	N/A	-12	-0.01	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	-12	-0.01	N/A	N/A	-12	-0.01	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	-12	-0.01	N/A	N/A	0	0.0	N/A	N/A
arduino:avr:mega	-6	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-26	-0.01	0	0.0	-26	-0.01	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-44	-0.02	0	0.0	-40	-0.02	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-34	-0.01	0	0.0
arduino:avr:uno	-8	-0.02	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-26	-0.08	0	0.0	-26	-0.08	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-34	-0.11	0	0.0	-32	-0.1	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-34	-0.11	0	0.0
arduino:sam:arduino_due_x_dbg	-16	-0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	-16	-0.0	N/A	N/A	-8	-0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	-8	-0.0	N/A	N/A	-8	-0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	0	0.0	N/A	N/A	-8	-0.0	N/A	N/A	0	0.0	N/A	N/A
arduino:samd:arduino_zero_edbg	-8	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-8	-0.0	0	0.0	-8	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-8	-0.0	0	0.0	-8	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-8	-0.0	0	0.0	0	0.0	0	0.0
arduino:samd:mkr1000	-8	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-8	-0.0	0	0.0	-8	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-8	-0.0	0	0.0	-8	-0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	-8	-0.0	0	0.0	0	0.0	0	0.0

Click for full report CSV

Board,examples/AP_SimpleWebServer<br>flash,%,examples/AP_SimpleWebServer<br>RAM for global variables,%,examples/CheckWifi101FirmwareVersion<br>flash,%,examples/CheckWifi101FirmwareVersion<br>RAM for global variables,%,examples/ConnectNoEncryption<br>flash,%,examples/ConnectNoEncryption<br>RAM for global variables,%,examples/ConnectWithWEP<br>flash,%,examples/ConnectWithWEP<br>RAM for global variables,%,examples/ConnectWithWPA<br>flash,%,examples/ConnectWithWPA<br>RAM for global variables,%,examples/MDNS_WiFiWebServer<br>flash,%,examples/MDNS_WiFiWebServer<br>RAM for global variables,%,examples/Provisioning_WiFiWebServer<br>flash,%,examples/Provisioning_WiFiWebServer<br>RAM for global variables,%,examples/ScanNetworks<br>flash,%,examples/ScanNetworks<br>RAM for global variables,%,examples/ScanNetworksAdvanced<br>flash,%,examples/ScanNetworksAdvanced<br>RAM for global variables,%,examples/SimpleWebServerWiFi<br>flash,%,examples/SimpleWebServerWiFi<br>RAM for global variables,%,examples/WiFiChatServer<br>flash,%,examples/WiFiChatServer<br>RAM for global variables,%,examples/WiFiPing<br>flash,%,examples/WiFiPing<br>RAM for global variables,%,examples/WiFiSSLClient<br>flash,%,examples/WiFiSSLClient<br>RAM for global variables,%,examples/WiFiUdpNtpClient<br>flash,%,examples/WiFiUdpNtpClient<br>RAM for global variables,%,examples/WiFiUdpSendReceiveString<br>flash,%,examples/WiFiUdpSendReceiveString<br>RAM for global variables,%,examples/WiFiWebClient<br>flash,%,examples/WiFiWebClient<br>RAM for global variables,%,examples/WiFiWebClientRepeating<br>flash,%,examples/WiFiWebClientRepeating<br>RAM for global variables,%,examples/WiFiWebServer<br>flash,%,examples/WiFiWebServer<br>RAM for global variables,%,examples/FirmwareUpdater<br>flash,%,examples/FirmwareUpdater<br>RAM for global variables,%
Intel:arc32:arduino_101,-12,-0.01,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,-12,-0.01,N/A,N/A,-12,-0.01,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,-12,-0.01,N/A,N/A,-12,-0.01,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,-12,-0.01,N/A,N/A,0,0.0,N/A,N/A
arduino:avr:mega,-6,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-26,-0.01,0,0.0,-26,-0.01,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-44,-0.02,0,0.0,-40,-0.02,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-34,-0.01,0,0.0,,,,
arduino:avr:uno,-8,-0.02,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-26,-0.08,0,0.0,-26,-0.08,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-34,-0.11,0,0.0,-32,-0.1,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-34,-0.11,0,0.0,,,,
arduino:sam:arduino_due_x_dbg,-16,-0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,-16,-0.0,N/A,N/A,-8,-0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,-8,-0.0,N/A,N/A,-8,-0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,0,0.0,N/A,N/A,-8,-0.0,N/A,N/A,0,0.0,N/A,N/A
arduino:samd:arduino_zero_edbg,-8,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-8,-0.0,0,0.0,-8,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-8,-0.0,0,0.0,-8,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-8,-0.0,0,0.0,0,0.0,0,0.0
arduino:samd:mkr1000,-8,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-8,-0.0,0,0.0,-8,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-8,-0.0,0,0.0,-8,-0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,-8,-0.0,0,0.0,0,0.0,0,0.0