How to get each device's IP address in Wi-Fi Direct scenario?

Question

Starting from ICS, Wi-Fi Direct is introduced. Normally, we use the WifiP2pManager class to operate on Wi-Fi Direct, but it seems that it can only retrieve the

Answer 1

I encountered the same problem. Since both devices know the group owner's ip, it is already possible to send a message to the group owner. The first message you send can contain the ip address of the other device; from then on, bidirectional communication is possible.

Here's a possibility for retrieving your ip in java:

private byte[] getLocalIPAddress() {
    try { 
        for (Enumeration en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) { 
            NetworkInterface intf = en.nextElement(); 
            for (Enumeration enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) { 
                InetAddress inetAddress = enumIpAddr.nextElement(); 
                if (!inetAddress.isLoopbackAddress()) { 
                    if (inetAddress instanceof Inet4Address) { // fix for Galaxy Nexus. IPv4 is easy to use :-) 
                        return inetAddress.getAddress(); 
                    } 
                    //return inetAddress.getHostAddress().toString(); // Galaxy Nexus returns IPv6 
                } 
            } 
        } 
    } catch (SocketException ex) { 
        //Log.e("AndroidNetworkAddressFactory", "getLocalIPAddress()", ex); 
    } catch (NullPointerException ex) { 
        //Log.e("AndroidNetworkAddressFactory", "getLocalIPAddress()", ex); 
    } 
    return null; 
}

private String getDottedDecimalIP(byte[] ipAddr) {
    //convert to dotted decimal notation:
    String ipAddrStr = "";
    for (int i=0; i 0) {
            ipAddrStr += ".";
        }
        ipAddrStr += ipAddr[i]&0xFF;
    }
    return ipAddrStr;
}

ip = getDottedDecimalIP(getLocalIPAddress());

Wrap this ip in a Serializable object and send it to the group owner like you would send any other object. Consider this the first step in your wifi-direct protocol... Now, the group owner also has an IP to send answers to.

This works for me, although I think it's weird that I had to implement this myself and I could only find the group owner ip easily (info.groupOwnerAddress.getHostAddress(); //with info a WifiP2pInfo instance). Maybe there is a comparable way to retrieve the ip of the other peers, but I couldn't find it. Please contact me if you do.

Good luck...