Running Flask dev server using HTTPS

Create a self signed certificate

openssl genrsa -out foobar.key 2048
openssl req -new -key foobar.key -out foobar.csr
openssl x509 -req -days 365 -in foobar.csr -signkey foobar.key -out foobar.crt

if os.environ.get("ENV_TESTING") == "True":
    context = (os.environ.get("CERT_PATH"), os.environ.get("KEY_PATH"))
    app.run(host='0.0.0.0', port=9090, ssl_context=context, threaded=True)

Bash script to notify me when a web site is up

One of the systems we depend on is down, and I wanted to get notified when it gets back up. And because I am lazy (Isn't that the motive for everything?) I wanted to write a script that checks it for me and mail me when the system gets back up.

Here is the script content:

curl -s -o "/dev/null" $1

if [ $? -eq 0 ] ; then

        if [ ! -f /data/epricer/utils/notified.status ] ; then

                echo "$1 is now up!" | mail -s "Website is up" $2

                touch /data/epricer/utils/notified.status

        fi

fi

This script takes two params, the first is the URL to check, and the 2nd is the email to notify. The scripts also creates a file when the server gets up, then check for it again when sending the notification, to prevent it from spamming my mail with thousands of "It is up" mails. I only need the notification once.

Save that in a file let's call /data/utils/notifyMe.sh. And make it executable. 

Then setup crontab to run this file periodically (for me it is every 10 mins) by issuing 

crontab -e

and adding the text below to a new line of the file 

10,20,30,40,50,59 * * * * /data/utils/notifyMe.sh https://mysystem.com myemail@domain.com

Save crontab and viola, you will be notified when the system is up. This took around 5 mins, but it is handy. 

Use DD-WRT to Join two wireless networks using a wireless link in Repeater mode

So me and my neighbour wanted to share a network, we both have existing separate wireless networks with multiple devices configured to use our networks. The most straightforward way to do that is to run a cable between our apartments (drill a couple of walls, get a long cable and run it from his router to mine, configure my router to work as an access point only with DHCP disabled) but because we were too lazy to do that, we decided to do this wirelessly.

I did some research, and I stumbled upon DD-WRT. DD-WRT is an open source linux based firmware for wireless routers. Although it is an open source project, it became so popular and so powerful that router companies like Buffalo manufactured and shipped routers that runs DD-WRT out of the box.

DD-WRT has plenty of features that I wanted to use, like having OpenVPN server and client, advanced DDNS capabilities, static NAT, and advanced repeater capabilities which exactly what I need.

Here is what I needed to do:

Pick a router that can run DD-WRT: I ended up picking LinSys E1200v2 http://amzn.com/B00AAU54TW. The router is cheap (20$), fully supports DD-WRT, and it has a nice wireless range. Edit: I take the "Fully supports DD-WRT" part back, it does support it fully on paper, but DD-WRT builds vary, some builds are stable enough to run everything perfectly, and some other builds will make your wireless network like a bird in a storm! For me build 25974 worked perfectly. 

Install DD-WRT on the router: I followed the instructions in the official DD-WRT wiki and install the same initial build, and it worked like a charm http://www.dd-wrt.com/wiki/index.php/Linksys_E1200v2. After I was done with the instructions I flashed this bigger more stable build 
ftp://ftp.dd-wrt.com/betas/2015/01-20-2015-r25974/broadcom_K26/dd-wrt.v24-25974_NEWD-2_K2.6_big-nv64k.bin. 
Important: when flashing dd-wrt builds, DO NOT SELECT TO RESET SETTINGS WHILE FLASHING. THIS WILL STOP THE ETHERNET PORTS FROM RUNNING. 

Configure the router: This is the fun part, DD-WRT has two different repeater modes: 

• Repeater bridged mode: repeats a wireless signal of a primary router while bridging the two networks together. This mode must disable DHCP on the secondary router and use DHCP only on the primary router. Basically making the two networks a single network with a Wifi signal booster installed on the network. In this mode devices on the primary network and devices on the secondary network can access each other directly. 
• Repeater mode: repeats a wireless signal of a primary router while keeping DHCP on the secondary router working and assigning IPs to its devices. In this mode the secondary router acts as a node in the primary router's network and uses NAT to bridge devices connected to it. In this mode devices on the secondary network can access devices on the primary networks directly, while devices on the primary network can only access devices on the secondary networks using port forwarding, and this is OK in my case so I picked this mode. 

Edit: Unfortunately after using DD-WRT for about 2 months. I have encountered instability issues, the router would unexpectedly disconnect all wireless clients and hang. I had to restart it to be able to connect again, this happend like twice daily. I ended up switching to Shibby Tomato, and it has been solid for almost a week now. I will write a follow up blog on Tomato. 

Deploying Android applications to a device without a USB cable (Hands-free development)

I just answered a question on stackoverflow that I think worth a blog. The asker is developing an Ionic app that uses a connected USB printer, and he was testing his app dong the following

1- Connect the device to his computer using USB
2- Deploy the app to the mobile
3- Disconnect the USB cable form the device
4- Connect the printer cable to the device
5- Test the app.

This sounded much to him and to me -as a lazy developer- but luckily I remembered hearing about adb over Wi-fi that allows deploying the apk file over Wifi network, and I wondered why would not this work with Ioinc, and it turns out it did work. Here is how the first time setup is done:

1. Connect your android device to your computer using a USB cable
2. From a command line run adb tcpip 1234 // or any port of your chosing
3. disconnect your android USB cable
4. run adb connect <your-phone-ip>:1234
5. Connect your printer using the USB cable

After that, he can simply test his app by doing  ionic run android to deploy your app and enjoy a cable-switching free development experience.