WiFi issue !

[PitHerm]

Arduino Ide RPI Pico W library 4.5.4 installed

two different WiFi's with DHCP and different SSID and different ip ranges

Same behavior with WiFIMulti or while doing manually if SSID no more available WiFi.mode(WIFI_OFF) then delay(500) then WiFi.mode(WIFI_STA) and at last WiFi.begin(ssid,passwd)

it establishes a connection , gets IP etc and this connection works
after connection lost and a new connection is established to another SSID IP address is not updated the Pico W stays with the address received by the first successful connection . On this case the new connection doesn't work cause the Pico address doesn't fit to the range of the new SSID.

[earlephilhower]

As a meta note, an issue title of "WiFi issue!" really isn't helpful for maintainers or users. Please try and give a more descriptive title for future issues here and elsewhere. It'll help you get support that much quicker...

Anyway, the way the Arduino WiFi interface is defined the existing accepted address should not be cleared on ::end. But, for WiFiMulti it can be assumed that we're not setting a static IP and manually force a DHCP probe. So we should force localIP to be 0 before attempting connections.

Give #2976 a try and report back (using WiFiMulti, not manual connection). If you manually want to swap nets, force a DHCP request by setting the config to 0,0,0,0 before WiFi.begin

[PitHerm]

As a meta note, an issue title of "WiFi issue!" really isn't helpful for maintainers or users. Please try and give a more descriptive title for future issues here and elsewhere. It'll help you get support that much quicker...

I will try be clearer in future but at last it is a WiFi issue while comparing the behavior of PicoW to ESP32/ESP8266

While running the simple code below it works fine on ESP32 and ESP8266 , they every time change their IP-address to the
IP range of the new connected network.
PicoW does not, it always sticks at the IP from the network connected at first.
Enable the line
WiFi.config(IPAddress(0, 0, 0, 0));
i tried your line WiFi.config(IPAddress(0, 0, 0, 0)); before and after wifi.begin and even the line
WiFi.config({ 0,0,0,0 }, { 0,0,0,0 }, { 0,0,0,0 }, { 0,0,0,0 });
nothing of that does make any changes on PicoW , same behavior like before.
like on ESP wifi.begin() should clear any values and do a new dhcp request.

#include <WiFi.h> /for ESP32 and PicoW
//#include <ESP8266WiFi.h> //for ESP8266

void setup() {
  Serial.begin(115200);
  delay(200);
  Serial.println("I'm Here");
  
  Serial.println("Connecting Wifi...");
  WiFi.begin("SSIDA","PASSWDA");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
  }
    Serial.println("");
    Serial.println("WiFi connected");
    Serial.println("IP address: ");
    Serial.println(WiFi.localIP());
  
  Serial.println("I'm Here");
}

void loop() {
  delay(10000);
  
  // Force DHCP request
  //WiFi.config(IPAddress(0, 0, 0, 0));
  
  WiFi.begin("SSIDB","PASSWDB");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("WiFi connected to: ");Serial.println(WiFi.SSID());
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  delay(10000);
  
  // Force DHCP request
  //WiFi.config(IPAddress(0, 0, 0, 0));
  
  WiFi.begin("SSIDA","PASSWDA");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("WiFi connected to: ");Serial.println(WiFi.SSID());
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  
}

Results:

PicoW:

07:36:51.050 -> WiFi connected
07:36:51.050 -> IP address:
07:36:51.050 -> 192.168.178.10
07:36:51.050 -> I'm Here
07:37:01.941 ->
07:37:01.941 -> WiFi connected to: PittyplatschGuests
07:37:01.941 -> IP address: 192.168.178.10
07:37:12.875 ->
07:37:12.875 -> WiFi connected to: pittyplatsch
07:37:12.875 -> IP address: 192.168.178.10
07:37:23.787 ->
07:37:23.787 -> WiFi connected to: PittyplatschGuests
07:37:23.787 -> IP address: 192.168.178.10
07:37:34.676 ->
07:37:34.676 -> WiFi connected to: pittyplatsch
07:37:34.676 -> IP address: 192.168.178.10
07:37:45.614 ->
07:37:45.614 -> WiFi connected to: PittyplatschGuests
07:37:45.614 -> IP address: 192.168.178.10

ESP32:

07:38:59.404 -> Connecting Wifi...
07:38:59.564 -> ...........................................>cutted<
07:39:02.087 -> WiFi connected
07:39:02.087 -> IP address:
07:39:02.087 -> 192.168.178.176
07:39:02.087 -> I'm Here
07:39:12.255 -> ...........................................>cutted<
07:39:13.576 -> WiFi connected to: PittyplatschGuests
07:39:13.576 -> IP address: 192.168.179.2
07:39:23.723 -> ...........................................>cutted<
07:39:25.518 -> WiFi connected to: pittyplatsch
07:39:25.518 -> IP address: 192.168.178.176
07:39:35.609 -> ...........................................>cutted<
07:39:36.969 -> WiFi connected to: PittyplatschGuests
07:39:36.969 -> IP address: 192.168.179.2
07:39:47.136 -> ...........................................>cutted<
07:39:48.415 -> WiFi connected to: pittyplatsch
07:39:48.415 -> IP address: 192.168.178.176
07:39:58.542 -> ...........................................>cutted<
07:39:59.824 -> WiFi connected to: PittyplatschGuests
07:39:59.824 -> IP address: 192.168.179.2
07:40:10.003 -> ...........................................>cutted<
07:40:11.243 -> WiFi connected to: pittyplatsch
07:40:11.243 -> IP address: 192.168.178.176
07:40:21.371 -> ...........................................>cutted<
07:40:22.691 -> WiFi connected to: PittyplatschGuests
07:40:22.691 -> IP address: 192.168.179.2
07:40:32.863 -> ...........................................>cutted<
07:40:34.144 -> WiFi connected to: pittyplatsch
07:40:34.144 -> IP address: 192.168.178.176

[earlephilhower]

Add a WiFi.end() before the config call. You can't change an IP after it's started.

[PitHerm]

Thanks , this works.

WiFi.end();
WiFi.config(IPAddress(0, 0, 0, 0));
WiFi.begin("SSIDA","PASSWDA");

maybe i do not understand every rule but for me it looks that this: WiFi.end(); WiFi.config(IPAddress(0, 0, 0, 0));
or something like this does WiFi.begin on ESP and should be integrated into WiFi.begin of PicoW i suggest.

15:16:07.179 ->
15:16:07.179 -> WiFi connected
15:16:07.179 -> IP address:
15:16:07.179 -> 192.168.178.10
15:16:07.179 -> I'm Here
15:16:23.824 ->
15:16:23.824 -> WiFi connected to: PittyplatschGuests
15:16:23.824 -> IP address: 192.168.179.4
15:16:40.203 ->
15:16:40.203 -> WiFi connected to: pittyplatsch
15:16:40.203 -> IP address: 192.168.178.10
15:16:56.680 ->
15:16:56.680 -> WiFi connected to: PittyplatschGuests
15:16:56.680 -> IP address: 192.168.179.4
15:17:13.199 ->
15:17:13.199 -> WiFi connected to: pittyplatsch
15:17:13.199 -> IP address: 192.168.178.10

[earlephilhower]

@JAndrassy any opinion here? Originally we forced DHCP request on every WiFi.begin call (since we 0-d out the netif ipaddress on WiFi.end). Now, we keep that DHCP lease until it times out even between WiFi.begins since the netif IPaddress is going to be preserved...

[earlephilhower]

Thinking about this some more, it does seem like when a link goes up any existing DHCP leases could possibly be wrong (we can't really know) so a re-request makes sense on ::begin. I have tested #2977 against your MCVE (where both nets were the same SSID but I changed the DHCP assignment on my router on-the-fly) and it does catch the new address when it ::begins in the loop. A DHCP request to the same network with an active lease should also return the existing address, so in the normal case this would also be OK.