esp-idf: Wifi roaming does not work (802.11k 802.11v 802.11r or client-side roaming) in STA mode (IDFGH-10713)

Hi @kapilkedawat : Ok, could you explain why the feature is not on the raodmap. Is it due to project priority reasons, or due to a technical restriction in ESP-Hardware?

@kapilkedawat as @xoores mentioned, the main problem is the disconnection of sockets while roaming.

Consider the following use case: ESP32 device is installed on a forklifter. Forklifter is constantly moving between access points. Now a client tries to load recorded data from the device via http. This operation will fail when the device is roaming while the http request is active. Of course, I can think about workarounds, but in my opinion, this should work.

So can you consider to change wifi stack NOT to close underlying LWIP connections while roaming?

@Saicharan67 : You can connect to a specific AP like this:

s_preferred_bssid contains the MAC, and s_preferred_channel contains the channel.

    wifi_config_t wifi_config;

    if ((err = esp_wifi_get_config(WIFI_IF_STA, &wifi_config)) != ESP_OK) {
        ESP_LOGE(TAG, "esp_wifi_get_config failed: %s", esp_err_to_name(err));
        return err;
    }

    memcpy(wifi_config.sta.bssid, s_preferred_bssid, sizeof(wifi_config.sta.bssid));
    wifi_config.sta.bssid_set = true;
    wifi_config.sta.channel = s_preferred_channel;

    if ((err = esp_wifi_set_config(WIFI_IF_STA, &wifi_config)) != ESP_OK) {
        ESP_LOGE(TAG, "esp_wifi_set_config failed: %s", esp_err_to_name(err));
        // try connect anyway
    }

    if ((err = esp_wifi_connect()) != ESP_OK) {
        ESP_LOGE(TAG, "esp_wifi_connect failed: %s", esp_err_to_name(err));
    }

Hi @KlausPopp , This methodology is called make-before-break. However we don’t have plans to implement it in near future. Only break-before-make is available with ESP devices.

Hello @kapilkedawat : Thanks for your reply. Why is it necessary to disconnect from the old AP first before connecting to the new AP? I monitored an iPhone while roaming. I does it absolutely seamless, no IP interruption occurs. I noticed that the IPhone reassociates with the new AP while it is still associated with the old AP. After some seconds, the old AP sends a disassociation request to the iPhone due to missing ACKs. Would such an approach be possible with ESP wifi stack?

Hello @xoores : I experienced the same problem. I am using ESP-IDF v5.1.1 and AVM Fritzbox mesh. I used a Raspberry PI and wireshark as a network sniffer. What I saw, is that the ESP sends a “BTM transition query” to the AP, but the AP ignores it. Thats why the STA does not roam. In other situations, the AP sends a BTM transition request (without a prior query from the STA), which causes the STA to roam.

For me, the big problem is, that it seems not possible with the current Wifi stack to perform a SEAMLESS roaming (i.e. without a connection loss when roaming). The wifi stack always disconnects from the old AP, and then connects to the new AP, which takes at least 2 seconds.

Espressif Team: Do you have plan to change this in the future?