Appendix; Sniffer Introduction - Espressif Systems ESP8266EX Programming Manual

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A.
A.1. Sniffer Introduction
For more details on sniffer, please refer to
A.2. ESP8266 SoftAP and Station Channel Configuration
Even though ESP8266 supports the SoftAP+Station mode, only one hardware channel can
be used for communication.
In the SoftAP+Station mode, the ESP8266 SoftAP will adjust its channel configuration to be
same as that of the ESP8266 Station.
This limitation may cause some inconveniences in the SoftAP+Station mode that users
need to pay special attention to, for example:
Case One:
1. When the user connects the ESP8266 to a router (for example, channel 6),
2. and sets the ESP8266 SoftAP through Wi-Fi_softap_set_config,
3. if the value is valid, the API will return true. However, the channel will be automatically
adjusted to channel 6 in order to be in line with the ESP8266 Station interface. This is
because there is only one hardware channel in this mode.
Case Two
1. If the user sets the channel of the ESP8266 SoftAP through Wi-Fi_softap_set_config
(for example, channel 5),
2. other Stations will connect to the ESP8266 SoftAP.
3. Then if the user connects the ESP8266 Station to a router (for example, channel 6),
4. the ESP8266 SoftAP will adjust its channel to be as same as that of the ESP8266
Station (which is channel 6 in this case).
5. As a result of the change of channel, the Wi-Fi connection of the Stations connected to
the ESP8266 SoftAP in Step Two will be disconnected.
Case Three
1. Other Stations are connected to the ESP8266 SoftAP.
2. If the ESP8266's Station interface has been scanning or trying to connect to a target
router, the ESP8266 SoftAP-end connection may break.
3. This is because the ESP8266 Station will try to find its target router in different channels,
which means it will keep changing channels, and as a result, the ESP8266 SoftAP
channel is changing, too. Therefore, the ESP8266 SoftAP-end connection may break.
Espressif
ESP8266 Technical
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Appendix A

Appendix

Reference.
2017.05