[GH-ISSUE #1429] Switching to DHCP mode #1222

New issue

Open

opened 2026-02-28 01:29:06 +03:00 by kerem · 5 comments

kerem commented

2026-02-28 01:29:06 +03:00

Owner

Originally created by @Alex-Trusk on GitHub (Jun 12, 2022).
Original GitHub issue: https://github.com/tzapu/WiFiManager/issues/1429

Hi.
Here is some algorithm (approach) of setting an IP I'm using.

Setting up default static IP/MASK/GW/DNS that are shown when config portal starts by calling
wifiManager.setSTAStaticIPConfig(_ip, _gw, _sn, _gw);
When config portal starts user surely has an opportunity to set his own required IP/MASK/GW/DNS or to choose DHCP method of setting an IP. To manage this I've added custom parameter: 0 - use static IP, 1 - use DHCP.
WiFiManagerParameter force_DHCP("F_DHCP", "1-Use DHCP 0-StaticIP", "0", 1);
After Save button was pressed, I'm checking force_DHCP parameter in callback
wifiManager.setSaveParamsCallback(AfterSaveParamCallback);
If force_DHCP is enabled I'm setting IP/MASK/GW = 0.0.0.0

_IPAddress n_ip, n_mask, n_gw, n_dns;
  n_ip.fromString("0.0.0.0");
  n_gw.fromString("0.0.0.0");
  n_mask.fromString("0.0.0.0");
  wifiManager.setSTAStaticIPConfig(n_ip, n_mask, n_gw);_

If IP equals "0.0.0.0" wifimanager would connect to AP using DHCP.
5. After exiting from AfterSaveParamCallback callback wifimanager returns to handlewifisave() function

`void WiFiManager::handleWifiSave() 
{
  #ifdef WM_DEBUG_LEVEL
  DEBUG_WM(DEBUG_VERBOSE,F("<- HTTP WiFi save "));
  DEBUG_WM(DEBUG_DEV,F("Method:"),server->method() == HTTP_GET  ? (String)FPSTR(S_GET) : (String)FPSTR(S_POST));
  #endif
  handleRequest();'

 // @todo use new callback for before paramsaves
  if (!_paramsInWifi && _presavecallback != NULL) {
    _presavecallback(); // CALLBACK is CALLED
  }

  //SAVE/connect here
  _ssid = server->arg(F("s")).c_str();
  _pass = server->arg(F("p")).c_str();

if(_paramsInWifi) doParamSave();

  if (server->arg(FPSTR(S_ip)) != "") {
    //_sta_static_ip.fromString(server->arg(FPSTR(S_ip));
    String ip = server->arg(FPSTR(S_ip));
    optionalIPFromString(&_sta_static_ip, ip.c_str());
    #ifdef WM_DEBUG_LEVEL
    DEBUG_WM(DEBUG_DEV,F("static ip:"),ip);
    #endif

Unfortunately after setting _sta_static_ip ="0.0.0.0" wifimanager will read IP settings from server rewriting IP stored in _sta_static_ip.

Is there is another way to connect using DHCP? Can you add another callback that will be called after String ip = server->arg(FPSTR(S_ip));?

Originally created by @Alex-Trusk on GitHub (Jun 12, 2022). Original GitHub issue: https://github.com/tzapu/WiFiManager/issues/1429 Hi. Here is some algorithm (approach) of setting an IP I'm using. 1. Setting up default static IP/MASK/GW/DNS that are shown when config portal starts by calling `wifiManager.setSTAStaticIPConfig(_ip, _gw, _sn, _gw);` 2. When config portal starts user surely has an opportunity to set his own required IP/MASK/GW/DNS **or** to choose DHCP method of setting an IP. To manage this I've added custom parameter: 0 - use static IP, 1 - use DHCP. `WiFiManagerParameter force_DHCP("F_DHCP", "1-Use DHCP 0-StaticIP", "0", 1);` 3. After Save button was pressed, I'm checking force_DHCP parameter in callback `wifiManager.setSaveParamsCallback(AfterSaveParamCallback);` 4. If force_DHCP is enabled I'm setting IP/MASK/GW = 0.0.0.0 ```c++ _IPAddress n_ip, n_mask, n_gw, n_dns; n_ip.fromString("0.0.0.0"); n_gw.fromString("0.0.0.0"); n_mask.fromString("0.0.0.0"); wifiManager.setSTAStaticIPConfig(n_ip, n_mask, n_gw);_ ``` If IP equals "0.0.0.0" wifimanager would connect to AP using DHCP. 5. After exiting from AfterSaveParamCallback callback wifimanager returns to handlewifisave() function ```c++ `void WiFiManager::handleWifiSave() { #ifdef WM_DEBUG_LEVEL DEBUG_WM(DEBUG_VERBOSE,F("<- HTTP WiFi save ")); DEBUG_WM(DEBUG_DEV,F("Method:"),server->method() == HTTP_GET ? (String)FPSTR(S_GET) : (String)FPSTR(S_POST)); #endif handleRequest();' // @todo use new callback for before paramsaves if (!_paramsInWifi && _presavecallback != NULL) { _presavecallback(); // CALLBACK is CALLED } //SAVE/connect here _ssid = server->arg(F("s")).c_str(); _pass = server->arg(F("p")).c_str(); if(_paramsInWifi) doParamSave(); if (server->arg(FPSTR(S_ip)) != "") { //_sta_static_ip.fromString(server->arg(FPSTR(S_ip)); String ip = server->arg(FPSTR(S_ip)); optionalIPFromString(&_sta_static_ip, ip.c_str()); #ifdef WM_DEBUG_LEVEL DEBUG_WM(DEBUG_DEV,F("static ip:"),ip); #endif ``` 6. Unfortunately after setting _sta_static_ip ="0.0.0.0" wifimanager will read IP settings from server rewriting IP stored in _sta_static_ip. Is there is another way to connect using DHCP? Can you add another callback that will be called after String ip = server->arg(FPSTR(S_ip));?

kerem commented

2026-02-28 01:29:07 +03:00

Author

Owner

@tablatronix commented on GitHub (Jun 13, 2022):

Not sure I understand, dhcp is the default. Are you allowing the user to enter ips?

have you tried just setting ips to 0

@tablatronix commented on GitHub (Jun 13, 2022): Not sure I understand, dhcp is the default. Are you allowing the user to enter ips? have you tried just setting ips to `0`

kerem commented

2026-02-28 01:29:07 +03:00

Author

Owner

@Alex-Trusk commented on GitHub (Jun 13, 2022):

Yes, user can enter static IPs. wifiManager.setShowStaticFields(true);
But also I want to give user a choice to set IPs directly or let DHCP server to assign IPs.
I consider two ways to set IP using DHCP.
First. Setting wifiManager.setShowStaticFields(false);, but user isn't allowed to set IP manually.
Second. User is allowed to set IPs manually, but if he wants to use DHCP he have to delete all IPs or set to 0. At least it is not convenient. Using simple radio buttons or checkbox is the easiest way. That’s why I want to check settings in Params Callback function. But _presavecallback() is called just before String ip = server->arg(FPSTR(S_ip)), so I'm unable to make successful IPs manipulations in callback.
I can make changes in wifimanager.cpp by myself and create new callback function. But I want to be sure that there is no other way to let user to switch between dhcp an static IP config.

@Alex-Trusk commented on GitHub (Jun 13, 2022): Yes, user can enter static IPs. `wifiManager.setShowStaticFields(true);` But also I want to give user a choice to set IPs directly or let DHCP server to assign IPs. I consider two ways to set IP using DHCP. First. Setting `wifiManager.setShowStaticFields(false);`, but user isn't allowed to set IP manually. Second. User is allowed to set IPs manually, but if he wants to use DHCP he have to delete all IPs or set to 0. At least it is not convenient. Using simple radio buttons or checkbox is the easiest way. That’s why I want to check settings in Params Callback function. But _presavecallback() is called just before String ip = server->arg(FPSTR(S_ip)), so I'm unable to make successful IPs manipulations in callback. I can make changes in wifimanager.cpp by myself and create new callback function. But I want to be sure that there is no other way to let user to switch between dhcp an static IP config.

kerem commented

2026-02-28 01:29:07 +03:00

Author

Owner

@tablatronix commented on GitHub (Jun 13, 2022):

Ah ok could do it in javascript. Ill take a look at moving that callback or a way to invalidate ips

@tablatronix commented on GitHub (Jun 13, 2022): Ah ok could do it in javascript. Ill take a look at moving that callback or a way to invalidate ips

kerem commented

2026-02-28 01:29:07 +03:00

Author

Owner

@tablatronix commented on GitHub (Jun 17, 2022):

I moved the presaveconfigcallback to after the ips wm vars are set, so maybe now they can be cleared before the wifi connect by clearing the wm _sta_static_ip value

@tablatronix commented on GitHub (Jun 17, 2022): I moved the presaveconfigcallback to after the ips wm vars are set, so maybe now they can be cleared before the wifi connect by clearing the wm _sta_static_ip value

kerem commented

2026-02-28 01:29:07 +03:00

Author

Owner

@tablatronix commented on GitHub (Jun 17, 2022):

I also added a presaveparams callback to deal with the new params seperation easier

@tablatronix commented on GitHub (Jun 17, 2022): I also added a presaveparams callback to deal with the new params seperation easier