Increasing ESP32 AP max connections

Question 1

It has already been asked how many clients can connect to an ESP32 AP, but the answer is far from clear; the best one is from a year and half ago (ESP32 AP max connections: 4 or 10?) :

The answer is as clear as any other EspressIf configuration data, it is 4 or maybe 5, or 8, or 12, 16 or even 20 (the same as a ESP8266!)

As I'm trying to move a project from the ESP8266 because it does not have enough AP connections, two questions can be asked :

what is the maximum number of AP connections supported by the 4.0 ESP-IDF framework ?
can it be increased in any way ?

Thank you.

Question 2

After some extensive testing with several modules (not just blindly trusting the documentation), here's what I found.

Short answer :maximum 10 AP connections for the ESP32 running ESP-IDF 4.0 (updated around 1st of march 2020), andno, it can't be increased (easily).

Details :

The maximum number of AP connections is defined somewhere in libnet80211, and can't be modified since I have no access to the source code.
when the 11th station tries to connect, libnet80211 printsI (39682043) wifi: max connection, deauth!, more or less like the ESP8266 for the 5th station
Changine theESP_WIFI_MAX_CONN_NUM (defined in esp_wifi_types.h:258) from 10 to anything else ends up in unpredictable behavior (I'm labelling this as unpredictable since without the libnet80211 code, it can't be reliably assessed).

I'm not giving up on increasing the number of stations yet, so maybe there'll be an update to this answer.

Question 3

According tothe documentation:

uint8_t max_connection
Max number of stations allowed to connect in, default 4, max 4

The WiFi interface and AP can support up to 10 connections in its internal structures, but that is only practical for WiFi Mesh usage (which doesn't use all 7 layers of the ISO model), and for actual WiFi station connections, which entails the allocation of far more resources (IP addresses, ARP tables, etc) only a maximum of 4 are supported.

If you need more connections I suggest you invest in areal access point / router which can deal with the network management for you (i.e., an access point or router which can do the DHCP and other networking housekeeping for you, leaving your ESP32 free to be a simple station).

Question 4

this is copy-paste from esp8266 doc

Question 5

No, it's aquote from the ESP32 documentation. Hence the link to the ESP32 documentation.

Question 6

Yes, it’s a quote from the documentation, but how reliable is the documentation ?

Question 7

If you search in the ESP-IDF files you will find ESP_WIFI_MAX_CONN_NUM=10,

Question 8

It looks like in 2016 they changed from a linked list to a static array for storage of connected stations. Since then the size of that static array has changed. For some reason the define started as 8, but the array was created as 8+2. Then the define changed to 10 and the array was also created directly from that define instead of adding 2. No idea what the significance of the "+2" was. However, the 10 is not for wifi. The 10 is for mesh. How many connections it supports, and how many areallowed are different things. The WiFi itself cansupport 10, which is fine for mesh use, but ...

stefanu 1311 silver badge4 bronze badges · Answer 1 · 2020-03-11 05:44:53Z

After some extensive testing with several modules (not just blindly trusting the documentation), here's what I found.

Short answer :maximum 10 AP connections for the ESP32 running ESP-IDF 4.0 (updated around 1st of march 2020), andno, it can't be increased (easily).

Details :

The maximum number of AP connections is defined somewhere in libnet80211, and can't be modified since I have no access to the source code.
when the 11th station tries to connect, libnet80211 printsI (39682043) wifi: max connection, deauth!, more or less like the ESP8266 for the 5th station
Changine theESP_WIFI_MAX_CONN_NUM (defined in esp_wifi_types.h:258) from 10 to anything else ends up in unpredictable behavior (I'm labelling this as unpredictable since without the libnet80211 code, it can't be reliably assessed).

I'm not giving up on increasing the number of stations yet, so maybe there'll be an update to this answer.

Majenko 106k5 gold badges82 silver badges139 bronze badges · Answer 2 · 2020-02-29 11:19:07Z

According tothe documentation:

uint8_t max_connection
Max number of stations allowed to connect in, default 4, max 4

The WiFi interface and AP can support up to 10 connections in its internal structures, but that is only practical for WiFi Mesh usage (which doesn't use all 7 layers of the ISO model), and for actual WiFi station connections, which entails the allocation of far more resources (IP addresses, ARP tables, etc) only a maximum of 4 are supported.

If you need more connections I suggest you invest in areal access point / router which can deal with the network management for you (i.e., an access point or router which can do the DHCP and other networking housekeeping for you, leaving your ESP32 free to be a simple station).

No, it's aquote from the ESP32 documentation. Hence the link to the ESP32 documentation.
Yes, it’s a quote from the documentation, but how reliable is the documentation ?
If you search in the ESP-IDF files you will find ESP_WIFI_MAX_CONN_NUM=10,
It looks like in 2016 they changed from a linked list to a static array for storage of connected stations. Since then the size of that static array has changed. For some reason the define started as 8, but the array was created as 8+2. Then the define changed to 10 and the array was also created directly from that define instead of adding 2. No idea what the significance of the "+2" was. However, the 10 is not for wifi. The 10 is for mesh. How many connections it supports, and how many areallowed are different things. The WiFi itself cansupport 10, which is fine for mesh use, but ...

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