networking - Android get IP-Address of a hotspot providing device

Question

I'm currently using

public static String getLocalIPAddress(WifiManager wm){
    return Formatter.formatIpAddress(wm.getConnectionInfo().getIpAddress());
}

to get the IP-Address of the executing devices. That works fine if the device is connected to a "common" wlan-network as well as the device is connected to a wifi network which is hosted by an other android device via hotspot. If the device is not connected to any wifi network "0.0.0.0" is returned (correct). But if the device is hosting a wifi network by providing a hotspot the methode is still returning "0.0.0.0". How can I get the real IP-Address of a hotspot providing device "in its own wifi-network"?

thx & regards

Answer 1

You're almost right, the default IP address of hotspot is 192.168.43.1 (If device maker didn't change.)

You can check the source code of Android framework (AOSP).

/frameworks/base/services/java/com/android/server/connectivity/Tethering.java /frameworks/base/wifi/java/android/net/wifi/WifiStateMachine.java

In the Tethering.java,

private static final String USB_NEAR_IFACE_ADDR      = "192.168.42.129";
private static final int USB_PREFIX_LENGTH        = 24;

// USB is  192.168.42.1 and 255.255.255.0
// Wifi is 192.168.43.1 and 255.255.255.0
// BT is limited to max default of 5 connections. 192.168.44.1 to 192.168.48.1
// with 255.255.255.0

private String[] mDhcpRange;
private static final String[] DHCP_DEFAULT_RANGE = {
    "192.168.42.2", "192.168.42.254", "192.168.43.2", "192.168.43.254",
    "192.168.44.2", "192.168.44.254", "192.168.45.2", "192.168.45.254",
    "192.168.46.2", "192.168.46.254", "192.168.47.2", "192.168.47.254",
    "192.168.48.2", "192.168.48.254",
};

Also, in the WifiStateMachine.java

private boolean startTethering(ArrayList<String> available) {                                 

    boolean wifiAvailable = false;                                                            

    checkAndSetConnectivityInstance();                                                        

    String[] wifiRegexs = mCm.getTetherableWifiRegexs();                                      

    for (String intf : available) {                                                           
        for (String regex : wifiRegexs) {                                                     
            if (intf.matches(regex)) {                                                        

                InterfaceConfiguration ifcg = null;                                           
                try {                                                                         
                    ifcg = mNwService.getInterfaceConfig(intf);                               
                    if (ifcg != null) {                                                       
                        /* IP/netmask: 192.168.43.1/255.255.255.0 */                          
                        ifcg.setLinkAddress(new LinkAddress(                                  
                                NetworkUtils.numericToInetAddress("192.168.43.1"), 24));      
                        ifcg.setInterfaceUp();                                                

                        mNwService.setInterfaceConfig(intf, ifcg);                            
                    }                                                                         
                } catch (Exception e) {                                                       
                    loge("Error configuring interface " + intf + ", :" + e);                  
                    return false;                                                             
                }                                                                             

                if(mCm.tether(intf) != ConnectivityManager.TETHER_ERROR_NO_ERROR) {           
                    loge("Error tethering on " + intf);                                       
                    return false;                                                             
                }                                                                             
                mTetherInterfaceName = intf;                                                  
                return true;                                                                  
            }                                                                                 
        }                                                                                     
    }                                                                                         
    // We found no interfaces to tether                                                       
    return false;                                                                             
}   

Therefore, the default value is 192.168.43.1 .