Android get IP-Address of a hotspot providing devi

问题:

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

回答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 .

回答2:

I tested a small couple of different devices and it seems that the hotspot providing device has always the IP 192.168.43.1 on its network. Can somebody please check/confirm this assumption?

回答3:

The Hotspot likely acts as a DHCP server. so,

To get IP address (server) of wifi hotspot after getting connected to it call method from remote (client)

intToInetAddress(wifiManager.getDhcpInfo().serverAddress);// get hotspot ip

then

public InetAddress intToInetAddress(int hostAddress) {
    byte[] addressBytes = {(byte) (0xff & hostAddress),
            (byte) (0xff & (hostAddress >> 8)),
            (byte) (0xff & (hostAddress >> 16)),
            (byte) (0xff & (hostAddress >> 24))};

    try {
        return InetAddress.getByAddress(addressBytes);
    } catch (UnknownHostException e) {
        throw new AssertionError();
    }
}

will return ip address of connected hotspot, and yes most default IP address of hotspot is 192.168.43.1