Exposing a VM on hosted WiFi hotspot for Google Glass

Background

Google Glass is famously frustrating to connect to a WiFi network. It doesn’t handle captive portals, or WiFi using Enterprise WPA2. I’ve also had consistent issues using MyGlass and QR codes to connect to Wifi.

I found myself in a situation where I had to connect Glass to a WiFi network on which a virtual machine was visible. My work’s corporate network was out of the question – it uses Enterprise WPA2. I would have connected my phone to the network and shared it to Glass via Bluetooth, but that was nixed for security reasons. So I had to set up a new network exclusively for Glass.

First thought – let’s just set up an Ad-Hoc wireless network on my laptop! But no, alas Android doesn’t support connecting to ad-hoc networks. Universe, why do you hate me so?

The solution

The solution involves a wireless-enabled Windows machine and VirtualBox – a program for running virtual machines.

An alternative to creating an ad-hoc network on your machine is to create a Wireless Hosted Network. This basically allows your Windows machine to act as a WiFi hotspot which can pass through a (wired) internet connection if you so wish.

My approach was to create a hosted network, connect my phone to it, then pass on the connection via Bluetooth. An admittedly insane chain of connections, but it’s all I had.

Create the WiFi network

  1. Open the Start menu and type “cmd”
  2. Right click and select “Run as Administrator”
  3. Type the following command:
     netsh wlan set hostednetwork mode=allow ssid=mynetworkid key=mypassword

Start the network

You’ll have to do this every time you start the machine, or alternatively set up a batch script to run this on startup.

  1. Type the following command:
     netsh wlan start hostednetwork

You should now see “mynetworkid” (or whatever you called it) in your list of wireless networks.

Create your VirtualBox image

  1. Install VirtualBox
  2. Create a new virtual machine (steps available here) – I’ve chosen to use a linux install
  3. Once your VM is created, go to Settings and choose Network
  4. Set up a Bridged Adapter
    1. Enable a network adapter
    2. Select Attached To: “Bridged Adapter”
    3. Select “Microsoft Virtual WiFi Miniport Adapter” as the Name – this is where the network you’ve just created is hosted.
  5. Start your VM up

Check connectivity

  1. On your Windows machine, open a command line and type:
     ipconfig

    A list of networks should be shown – one of which should be called “Wireless LAN adapter Wireless Network Connection”. Note down the first 9 digits of the IP address listed under this e.g. 192.168.173

  2. In your VM, run the following command:
     /sbin/ifconfig

    And note the networks and IPs that are listed. If no other networks were set up, your eth0 network should have an IP where the first 9 digits of the IP address matches those you noted down earlier. That means that they’re running on the network.

  3. For a laugh, ping your VM from your Windows machine, using the IP address from the previous step. This will confirm that your VM is addressable and contactable from your Windows machine. Given that your Windows machine is now broadcasting a wireless network, that means that the VM should be contactable to anyone on the network too.

Ping your VM from your Android device

As the penultimate proof, try pinging your VM from your Android device.

  1. Install an app which will let you run a ping command (I used PingTools)
  2. Ping the IP address you pinged previously

This should also show a response. And now we’re on the home straight.

Write some Glass code to contact your VM

You can do this however you wish. I wrote some very simple ping code to prove that Glass – once paired to my phone – was sharing the same internet connection as the phone, and the Windows machine, and as the VM.

There are tons of ways of doing it – for example:

InetAddress server = InetAddress.getByName("192.168.173.123");
if (server.isReachable(10000))
{
         // It’s contactable!
         celebrate();
}

Conclusions

That was much, much harder than it should have been. Alternatives I didn’t attempt:

  • Buying a router and broadcasting my corportate ethernet through it
  • Getting a company-approved phone that could have connected to the Enterprise network
  • Binning my Google Glass

PS – Many thanks to this post which acted as a great reference. It’s also worth checking out if you need to pass through internet via your hosted network.

How to invoke a SAS macro stored in a catalog

Having not done the Advanced Base SAS certification, this was a nightmare to work out. I’m documenting it here for my own future use, and to help anyone else who found themselves in the same situation as me.

What situation was that?

SAS Social Network Analysis can create networks from input data, and to do so it makes use of a pre-compiled “link macro” which is bundled with SNA. This link macro needs to be invoked from a base SAS program, but to do that, you need to tell SAS where to find it.

Note – There were literally zero Google hits for the exact name of this link macro. In case you’re curious, it’s called % sfs_net_main_link_macros.

Anyway I eventually found the location of these macros, in a catalog file.

Note – Not easy to find, and not documented. If anyone is in the same situation as me, it was in my <SASHome>\SASFoundation\9.3\snamva\macros folder. The macros are compiled into the sasmacr.sasb7cat file.

So I have a catalog file, how do I invoke the macro held in it?

Once you know, it’s very very simple.

  1. Copy the catalog file into your working directory
  2. Add a libname statement pointing to this working directory
  3. Use the SASMSTORE option

In other words your code should have the following statements:

libname mylib "D:\mylocation";
OPTIONS MSTORED SASMSTORE=mylib;

This will make the next invocation of the macro succeed, since SAS now knows it’s in your libname directory.

Removing duplicate rows in base SAS

If you ever need to remove duplicate rows from a SAS dataset, here’s an approach I use quite often.

Get your data.

Let’s assume it’s in the following format:

ID Name
123 John
456 Bob
123 John

Sort your data.

/* Step 1 - Sort data */
proc sort data=my_lib.my_dataset;

   /* Sort by a field which you want to be unique, 
   and which will be the same for duplicate rows */
   by id; 

run;

Which should give you the following:

ID Name
123 John
123 John
456 Bob


Remove Duplicates

Now that the data is in order, we can remove the duplicates, by only ever keeping the first entry which matches our unique ID.
-.

/* Step 2 - Get rid of duplicates */
data my_lib.my_dataset;

   /* Iterate through this dataset row by row */
   set my_lib.my_dataset;
   /* Grouping each row by the field we sorted on */ 
   by id; 
   /* And only keep a row if it’s the first */
   if first.id; 

run;

ID Name
123 John
456 Bob


Tadaa!

What happened there?

This approach has 3 facets:

  1. Grouping
  2. SAS’ special first.variable
  3. SAS’ feature of only appending (or “outputting”) a row to a dataset if there are no non-assignment statements which evaluate to false.


Grouping: So we effectively rearranged our data so that all identical IDs were grouped together. Given that the rows are identical and you only want to keep one of them, we choose to keep the first of each group.

First.variable: During execution, SAS will iterate through each row of my_data_set and adding it to a new dataset (which it will eventually overwrite my_data_set with). During each iteration, if it hits a row with the first use of an ID value (for example, 123), it will set first.id to true. On the next run, because it’s already seen the value 123 before, first.id is set to false. This gives us a handy flag which will only ever be toggled on unique rows.

Funny Statement Stuff: So how do we flag to SAS that when this value is set to true, to keep the row? When evaluating a data row if at any point we make any floating statement (i.e. not assigning a variable, or in an if or do loop) which evaluates to false, SAS will take that as a sign that it shouldn’t output that row i.e. in this case, it shouldn’t keep it.

So in simple terms, we’re saying – if you’ve seen this value before, don’t save it again.