A good diagnostic tool for any sysadmin is a port scanner to ensure a firewall is working as intended to open or close ports. When you want a quick and dirty scanning tool, there are some great free apps in the Market to do the trick. A quick search in the Market shows two apps which seem to be popular: OscanO and Port Scandroid.
This free app in the Market was written by Rich Jones of NewFreedomApps, found at http://www.thenewfreedom.net/ and the app is described by the author like this:
Port Scandroid is a port scanner for Android. It displays the reachability of a range of ports for a given host.
A scan on a 3G network may report some interesting false positives, so run it over wifi if you need accurate results.
By Rich Jones
Source code is available under GNU GPL:
The latest version is v1.0.0 and is only a 50.53KB download. It has a solid 4-star rating from 93 ratings, and feedback from users stop about August 2009. The only security permission is full Internet access.
Using the App
Starting the app shows some preset options to scan google.com for 133 ports. Hitting the Back button to clear the keyboard, then hitting the Menu button shows a single option: About. Tapping on it loads some information about the app in a scrollable area. There’s a black gap at the bottom of the screen which I’m guessing is a broken ad.
Scanning 133 ports on google.com took a few minutes, and only port 80 was open on the 133 ports scanned. At the end of the list was a summary, which would probably be better served at the top of the list instead.
It’s a free app and functional, and very simple and takes up very little space when installed. The description, however, encourages users to use Wifi but without manually shutting off 3G within Android, it becomes difficult to tell whether the app is using 3G or Wifi. The app does run a little slow, but in my own sysadmin experience, a slower scan can sometimes be more thorough.
This is another free app, this one written by “letufindme” (let you find me), is an equally small 49.42KB download, and is version 1.31. It has had 5,000 to 10,000 and has a 3.5-star rating from 111 users, and describes itself like this:
Slight update for cupcake.
Check out the Pro version for additional features.
Network port scanner. If you don’t know what a port or an IP address is, then don’t download this. It will be a waste of your time. Really only works on WIFI.
There is no web site URL for the developer within the Market description. User comments like ‘pgorny’ say “My ISP blocks most of the ports. Now I finally have a possibility to verify what’s blocked, from inside the building’s LAN.” (5 stars), and ‘fiziks’ saying “Doesn’t scan local topology, so discovery limited to known IPs or manual guessing.” (2 stars) and ‘MrHaanMan’ saying “Can't stop scan once started. doesnt detect pc presence first. Needs functionality to search across a whole subnet for ports” (2 stars).
The security settings for the app include needing full Internet access, and says it will prevent the phone from sleeping. After installing the app, the icon calls the app “OscanO LITE”
Using the App
This app appears to force the user into landscape mode. The opening screen shows a start and end port, what appears to be a hostname field, and a 'current port’ field which is updated with the current port being scanned but is not selectable or editable by the user.
Scanning google.com did a DNS lookup to scan an IP, and took about as long as Port Scandroid. Unfortunately there’s a slight bug in the software that cuts off the final line of data. Also, this app appears to lack a count of ports which were open or closed.
Before I forget, there’s a single submenu but only has two settings: to close the app, and to clear the current results screen.
This app runs at about the same speed as Port Scandroid, and also lacks the ability to discern whether it’s using 3G or Wifi.
Both of these apps are free, small, and appear to operate equally quickly. Both apps recommend that users use Wifi yet neither app allows the users to shut off 3G nor makes any indication about which network is being used when both 3G and Wifi are enabled.
Of course, the biggest failure on an app like this is doing a scan when inside a data center where you may not have either 3G service OR Wifi access, but there’s little that an app developer can do about that shortcoming.
Do you have a favorite port scanner?