Finding SSID of a wireless network with Java

问题:

We're doing a project coded in Java (compiled for JRE 1.6) and need some help with a little but apparently complicated feature: We want to do a certain action when a specific wireless network is connected e.g. when the connected SSID=="myNetworkAtHome" or similar.

After looking through this site, google and the Java documentation we have come a little closer. After looking at the code here: http://download.oracle.com/javase/tutorial/networking/nifs/retrieving.html

It seems we were getting close but it hits a deadend, all the interfaces seems to be connected to "net0" through "net13" (on my laptop that is.) And we're unable to get the SSID out of any interface at all. I do realise the code in the example is only giving the interface names and not connected networks, but it doesn't seem to offer a way of fetching the connected network information.

Any help on this would be extremely helpfull!

Regards Martin NJ

回答1:

You can't access this low-level details of the network in Java. You can get some details of the network interface with the NetworkInterface class but if you see at the provided methods, no one is related to Wifi networks nor any way to get the SSID is provided. As pointed below, you should use some native functionality through calling a native library with JNI or by calling a OS tool with Runtime.

Java is not designed to do that kind of things, is hard to implement in a platform-independent way and any hardware-level detail can not be managed in Java by principle.

Same applies to other networks like 3G, GPRS... the application should not be aware of the connection type nor its details. Java can only manage things at the Transport (TCP) level, not the network (IP) not Link (3G, Wifi, Ethernet...), so you can only manage sockets.

回答2:

You'll have to resort to a JNI solution. There's something available at http://sourceforge.net/projects/jwlanscan, but that only works for Windows systems. Or you could do it the ugly way and use Runtime.getRuntime().exec(...) and use the command line tools available for your OS (*nix = iwconfig) and resort to parsing.

回答3:

 ArrayList<String>ssids=new ArrayList<String>();
    ArrayList<String>signals=new ArrayList<String>();
    ProcessBuilder builder = new ProcessBuilder(
            "cmd.exe", "/c", "netsh wlan show all");
    builder.redirectErrorStream(true);
    Process p = builder.start();
    BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
    String line;
    while (r.read()!=-1) {
        line = r.readLine();
        if (line.contains("SSID")||line.contains("Signal")){
            if(!line.contains("BSSID"))
                if(line.contains("SSID")&&!line.contains("name")&&!line.contains("SSIDs"))
                {
                    line=line.substring(8);
                    ssids.add(line);

                }
                if(line.contains("Signal"))
                {
                    line=line.substring(30);
                    signals.add(line);

                }

                if(signals.size()==7)
                {
                    break;
                }

        }

    }
    for (int i=0;i<ssids.size();i++)
    {
        System.out.println("SSID name == "+ssids.get(i)+"   and its signal == "+signals.get(i)  );
    }