Category Archives: Signposts

Data Collection for Latency, Goodput & Jitter – Demo Pt 5.2

Everyone who I have spoken to about my work since yesterday, has asked me the same question. Why are you writing this in Java ? The answer is that I am going on the Google European Android Development Camp in a few weeks so I am using Java were possible in my work so that I can get familiar with the basics again.

To ensure that the server (my laptop) and the client (my android phone) can address each other I ensure that they are behind the same NAT so that private IP addresses can be used. This ensures that both devices can initialize an connect with the other

My Java code for analyzing and comparing Signpost Diagnostic Application to the results generated by Iperf and Ping, requires the following files:

  • SignOutput.txt – this is generated by the Signpost Diagnostic Application, It can be generated by:
    • Hard coding the server IP address into the application code, found here
    • Uninstall previous versions of the application and connect the android phone via USB
    • Within eclipse, load the application onto the android phone
    • cd into Downloads/android-sdk-linux/platform-tools
    • In another terminal, cd into the location of the demo server and start server using ./server.native
    • use “./adb logcat-s SIGPST >> SignOutput.txt”
    • The location of the file SignOutput.txt is now Downloads/android-sdk-linux/platform-tools, copy the file to /TestingSignpostAppOutput
  • IperfOutput.txt – this is generated by a remote shell on the Android phone, it can be generated by:
    • (In terminal 1) cd into Downloads/android-sdk-linux/platform-tools
    • connect android phone via USB
    • use “./adb shell” to start a remote shell
    • in another terminal (terminal 2), cd into /TestingSignpostAppOutput so output file is loaded straight into correct directory
    • (In terminal 2) use  iperf -s -u >> IperfOutput.txt
    • (In terminal 1) use iperf -u -c {insert laptop IP}
  • PingDownstreamOutput.txt – this is generated by the server sending pings to the client (the android phone), it can be generated by:
    • cd into  /TestingSignpostAppOutput so output file is loaded straight into correct directory
    • Run a bash script containing the following:
    • #!/bin/bashfor i in {1..10}
      ping {insert phone IP} -c 10 -n -q >>


  • PingUpstreamOutput.txt – this is generated by the client (android phone) sending pings to the server, it can be generated by:
    • cd into Downloads/android-sdk-linux/platform-tools
    • Save a bash script (lets call it pingUp) containing the following
    • #!/bin/bashfor i in {1..10}
      ping {insert laptop IP} -c 10 -n -q >>


    • Connect android phone via USB and copy script to SD cards using  ./adb push pingUp / sdcard/   “
    •  use “./adb shell” to start a remote shell
    • In the remote shell cd into /sdcard
    • In the remote shell run the script using ./pingUp
    • exit the remote shell
    • cd into  /TestingSignpostAppOutput
    • copy the PingUpstreamOutput.txt file to the laptop from the android phone using “./adb pull /sdcard/PingUpstreamOutput.txt

Once you have generated all of these files then you can run my program found here which should output the average true and estimated latency, goodput and jitter.
The code in is still incomplete and untested, I also have not yet tested my instructions for generating the correct files at the correct locations for the java code to be ran. I will be doing this testing next…

Data Collection for Latency – Demo Pt 5.1

Now its time for me to collect data from the Signpost Diagnostics Application and Iperf to see if there is a statistically significant difference between the Latency and Goodput data from the two applications. [Jitter will soon be added to the application so I will need to go back the test that]


Part A – Data from Signpost Application

  1. Connect the android phone (the client) and laptop (the server) to Internet in such a way that they are behind the same NAT box, so the client can initiate a connection with the server from a private IP address
  2. Set up the OCaml Server running on my laptop
  3. Change in client IP address in the client code and load onto android phone
  4. Running client with server, collecting data whilst viewing output from log files

Part B – Latency data from Ping

  1. Workout how to send pings bothways
  2. Workout how to use ping to get RRT bothways
  3. Collect some data on latency

Part C – Compare Data from Signposts Application and Ping

  1. Extract sufficient data from both methods
  2. Get data from both method into a suitable format
  3. If required, convert units for latency so all data in same units
  4. Compare data
  5. Answer the Question: Is there a significant difference between the data collected by Ping (assumed to be accurate) and the Signpost Application


Part A

I’ve just been send the most recent version of the Signpost Diagnostics Application as a .apk file. I uninstall the old version of the application using the Android GUI and install the new version using:

cd /android-sdk-linux/platform-tools
./adb install ~/Downloads/SigcommDemoAndroid.apk

I quick come to realize that the above is stage is useless. It will correctly install an application from the .apk file but I need to be able to edit the code of the application so that I can set the client IP address at a later stage

I connect both the client and server to the same Wi-FI network so that the client will be able in initiate an connection with the server

As per usual, to start up the OCaml Server, I will do

cd Downloads/sebastian-SignpostDemo-53ebd3e/SignpostServerOCaml/

I uninstalled the last Signpost Application, change the IP address in the code and load onto phone, via Eclipse using the run as dialogue.

Pressing start on the Android application triggers a connection to be initiated with the server, this is successful as the sever outputs a link detailing the android phones name, IP address and port number used.

I can view the logs for this application live, using:

cd  Downloads/android-sdk-linux/platform-tools

./adb logcat-s SIGPST

To filter the output of logcat, I use the arguments -s SIGPST, this gives me a log output such as:

I/SIGPST  ( 1520): Received Latency Upstream: 25500
I/SIGPST  ( 1520): Received Goodput Downstream: 4026
I/SIGPST  ( 1520): Received Latency Downstream: 6008
I/SIGPST  ( 1520): Received Goodput Downstream: 1262925
I/SIGPST  ( 1520): Received Latency Upstream: 49000
I/SIGPST  ( 1520): Received Goodput Downstream: 4787
I/SIGPST  ( 1520): Received Latency Downstream: 10376
I/SIGPST  ( 1520): Received Latency Upstream: 50000
I/SIGPST  ( 1520): Received Goodput Downstream: 2735
I/SIGPST  ( 1520): Received Latency Downstream: 17004
I/SIGPST  ( 1520): Received Latency Upstream: 46500
I/SIGPST  ( 1520): Received Goodput Downstream: 4461
I/SIGPST  ( 1520): Received Latency Downstream: 4463
I/SIGPST  ( 1520): Received Goodput Downstream: 799720
I/SIGPST  ( 1520): Received Latency Upstream: 51000
I/SIGPST  ( 1520): Received Goodput Downstream: 3684
I/SIGPST  ( 1520): Received Latency Downstream: 6875
I/SIGPST  ( 1520): Received Latency Upstream: 307000
I/SIGPST  ( 1520): Received Goodput Downstream: 4670
I/SIGPST  ( 1520): Received Latency Downstream: 8749
I/SIGPST  ( 1520): Received Latency Upstream: 16500
I/SIGPST  ( 1520): Received Goodput Downstream: 2652
I/SIGPST  ( 1520): Received Latency Downstream: 6795
I/SIGPST  ( 1520): Received Goodput Downstream: 24060150
I/SIGPST  ( 1520): Received Latency Upstream: 72500
I/SIGPST  ( 1520): Received Goodput Downstream: 4190
I/SIGPST  ( 1520): Received Latency Downstream: 6809

A quick code inspection, highlights that the latency values are divided by 1000 to be converted into secs, which means that the latency values here are in ms
I will look at how to convert this to a more convenient form in part 3

I can append the output to the file Signoutput.txt using “>> Signoutput.txt”

I have added a sample of Signoutput.txt here 

Part B

I open a remote shell on the android phone using ./adb shell, I then use the ping unix commend from the client to the server, and i get an output such as

24 packets transmitted, 24 received, 0% packet loss, time 23070ms
rtt min/avg/max/mdev = 35.614/90.183/297.302/51.944 ms

The latency will be half the RRT so here it is 45.0915 ms

Then repeating the test from the server to the client and i get an output such as

43 packets transmitted, 40 received, 6% packet loss, time 42070ms
rtt min/avg/max/mdev = 33.371/93.812/241.825/45.579 ms

So the latency is similar to before at 46.906 ms

Now I want to collect the data from the ping output, so I wrote the following bash script to do this:


for i in {1..10}
ping -c 10 -n -q >> Pingoutput.txt;

This sents 100 pings, in 10 sets of 10 and sent the results of the 10 test to a file called Pingoutput.txt
The first line “#!/bin/bash” mean that this is a bash script, the ping argument “-c 10” means said 10 pings and “-q” means quiet output. >> means append to file.

I’ve added a sample of Pingoutput.txt here

Part C

To analysis the output files, I have written the Java code here. Currently this code is untested

Getting Client & Server Talking – Demo Pt 3

Now I have an Android phone running the client and my laptop running the server, its time to get them taking.

A quick inspection of the client code shows the line “public static final int [] IP_ADDR = {128,2362,110,172}; ” I change this to the IP address of my laptop and reload the code onto my android phone.

I launch the server on my laptop, the client on the Android phone and here the troubleshooting begins. Nothing appears to happen on either the client or server so I:

  1. check the network connection on both client and server  ✓
  2. un-install the client application and re-install it ✓
  3. check the IP address of the server is correct ✓
  4. Try running client on emulator ✓ just got the exact same problem

Taking a closer look at the IP address used:

I tried to find out the IP address of the server by visiting here but i thought that I should try to take a more technical approach. Visiting connection information in Ubuntu gives me a different IP address. Now I’m fairly sure that my server is behind a NAT as is my client.

Initally I assume that the different IP address are caused by the NAT, therefore the IP address from the website, is my public IP address (the IP address of the NAT) and the IP address given to my by my OS is the private IP address, that I am referred to by machines also behind the NAT.

This explaination fails to explain why using the IP address from the website didn’t work and the IP address given to me by my OS doesn’t have the normal structure that I would accociate with a private IP address.

So I now repeat my initial test using the different IP address (previously I used the address provided by a website and now I am using the one provided by the OS) and it works on both the android phone and the emulator.

But by use of the word “works” I mean that the server recognises that a client has connected and the GUI on the android client provides graphs showing latency and goodput, it unfortunately doesnt mean that I’ve yet found a good way to extract the data to make a comparision to the data provided by Iperf to test accuracy and reliably, on the assumption that Iperf will always produce accurate results that we can assume to be the true value.

The next useful step will be to continue to explore why this IP address works and the other one doesn’t. As the client and server are now able to connect I can test if this IP address is working only because both client and server are behind the same NAT or is there something more complex going on. Currently both the laptop and android phone are making use of the same Wi-FI network, so the next step in testing if this will work when the client and server are not behind the same NAT is to change the network that either is using.

The plan for testing with would be:

  • move server onto another WiFi network
  • find out new IP address and update client code
  • test if emulator can connect to server, it should do as it used same network connection as the host computer, which in this case is the server
  • test if android phone can connect to server, it should not as its now not behind the same NAT as the server
  • move the android phone onto the other WiFi network
  • test if android phone can connect to server, it should now be able to

As this test is not critical for now, I will move onto Part 4 next week, where I get Iperf collecting the same data between the android client and then compare the data collected

Running the Android Client – Demo Pt 2.1

An update for you on my progress on test the code to measure network performance between an android phone and a computer running a server written in Ocaml. So far, I have run the server and the client separately but not yet got them communicating. As explained in part 2 of this series, I decided to set up Eclipse with ADT Plugin on my desktop after getting some weird errors on my current laptop set up of Eclipse and ADT. The details of the problem are available here on There has been no clear solution to the problem. Therefore I have had to totally remove my install of Eclipse and ADT, so that I can start all over again.


I’ve also been distracted the last few days by this piece of new kit, the DreamPlug. We are using it as part of the upcoming Signposts Demo at SIGCOMM in Helsinia.I will write an article on it soon

Finally I’ve fix my Eclipse set-up and I’m now able to load the client code onto the Android phone and run the server on my laptop. Part 3 will be coming very soon.

Also on a personal note, I am 20 today…

Running the Ocaml Server – Demo Pt 1


I’ve got some code here and here in OCaml & Java, that I have been tasked with running, testing and fixing. I’ve already taken a look at the basic syntax but now its time to get to grips with some the libraries and related packages that Signposts makes use off.


The first thing that took me by surprise was the number of files in the repo, considering that this is suppose to be a fairly straight forward project.


The repo contains a file called “_oasis”, which on closer inspection includes a collection of metadata on the project. OASIS is a tools to integrate a configure, build and install system into an OCaml project. The _oasis files tells me that the entry point for the program is “” and the build dependences are the findlib packages lwt.syntax, lwt.unix, re, re.str.
The creater of the program will have ran “oasis setup”, which has generated, _tags and

According to the instructions for OASIS you can configure, build and install the Ocaml program using:

  • ocaml -configure

  • ocaml -build

  • ocaml -install


The file makes use of Re_str and two of the biuld dependences are the findlib packages re and re.str. I have found the packages here on github. Re stands for Regular expression and ocaml-re is a regular expression library doe Ocaml (that is still under development). This project has also made use of OASIS and installs without a problem

Compiling the Code

I cd into the directory and run ocaml -configure, ocaml -build and ocaml -install. This generates a new dirctory “_biuld” and a new link to an executable in _biuld

Running the Code

I run a link to the execuated in _biuld and it return the following error:
Fatal error: exception Unix.Unix_error(50, “bind”, “”)
This means that the socked that the code is try to bind to is already in use. I inspected the code, identified the ports that were being used and ran “sudo netstat -ap | grep ‘: ‘ “. This identified a process already using the port, the process was in fact an earlier attempt to run the project. I identified the process ID and killed the process, re-running “sudo netstat -ap | grep ‘: ‘ “ showed that the port was now free. I can now happily run the executable in the _build directory. As this is a client-server implementation, I now need to move my attention to the client code

Running the Android Client – Demo Pt 2

[ Sorry but this is part 2 in the series, I have completed part 1 but will not be able to upload the article until tomorrow ]

This is the 2nd part of a series on my taking a look at the code here, to test it and then improve it if required. In part 1, I ran the Ocaml server on my laptop. In this part, I run the android client. Tomorrow (Monday), in part 3 I am going to get the client and server communicating. On Tuesday, I will hopefully collect some data that I can then extract in some suitable format. On Wednesday, I hope to run Iperf between my client and server to collect data and extract in some suitable format. On Thursday, I hope to have a day of collecting data using both the GitHub code and Iperf. Finally on Friday, I hope to use a statistics package such as MatLab to compare the data collected and see if there is a statistically significant difference.

Since I have managed to mess up my eclipse/android install (see part 1), this gives me a perfect excuse to set up eclipse with ADT Plugin on my desktop. I’ve also got my hands on a different android phone, since the code that testing was designed for API 10. The phone info is as follows:

Model: HTC Hero Andriod Version: 2.3.7CPU: ARMv6- compatible processor #34Available memory: 190MBMod Version: CyanogenMod-7.2.0-RC1-UNOFFICAL
Build Number: GWK74


The stages in setting up the Android ADK, Eclipse and loading the code that I’m testing on the Android device (spec above)

  1. Download the Android SDK (Software Development Kit)
  2. The SDK only installs the SDK tools so to install other parts of the SDK, I’ve got to open up the Andriod SDK Manager, this is done by cd’ing into the tools/ directory and executing android SDK
  3. To develop an Andriod app, I need to download the lastest Android SDK Platform-tools and at least on Android platform. The platform that I want is the one associated with Android 2.3.7 and API 10, I’m going to get the related SDK Platform. Documentation and System image.
  4. Download and install the latest Eclipse Classic
  5. Add the source of the ADT Plugin to the Repository in Eclipse and download the Developer Tools in via Eclipse
  6. Specify the location of the Android SDK directory in the Preferences panel of Eclipse
  7. Create a AVD (Android Virtual Device) in Eclipse with target platform 2.3.7 and API 10
  8. Download the code that I’m testing from GitHub
  9. Import the code into Eclpise
  10. Test Code on the AVD
  11. Plug in Android phone and test code on the Andriod phone



The Android SDK is avaliable from the Android Developer Site, the package for Linux is called android-sdk_r20-linux.tgz.

The download comes as a .tgz file, this can be extracted using: tar -zxf android-sdk_r20-linux.tgz after using cd to move to the directory that you downloaded the file to.

I’ve found that its useful the learn as your going along, the purpose of the arguments that you are passing to programs, so that you can then easily adjust the arguments in future to suit your needs. Using man tar, explains that -z means filter archive through gzip, -x means extract the filesand -f means that your next going to give the file name.I would highly recommend that when following tutorials with Unix commands that you use man to look up what the executable and its arguments do.


As with the last time I installed Android SDK, to launch the Android ADK Manager, I need to enter ./android SDK instead of android SDK. This then appears to work fine, but I would still be interested as to why I didn’t work as expected.

[To clarify This command is entered after you use cd to move into android-sdk-linux/tools]


I selected the required packages (that I’ve listed in the plan above) and download them, simple as.


(Read this whole paragraph before beginning to download Eclipse) I download Eclipse Classic 4.2 for 32 bits as a .tar.gz file and extract the file (like before using tar -zxf eclipse-SDK-4.2-linux-gtk.tar.gz ). To install Eclipse, I cd into the new eclipse directory, to find no configure file, so my normal method of installing from .tar.gz files, of using ./configure && make && sudo make install will now not work. I little bit of research highlights that installing eclipse its not as straightforward as it might seem and the best approach for integration into Ubuntu is to get it from the software center, though I would prefer to continue to use the command line, I’m happy to leave it for now and return to this point at a later date


I start up eclipse, select my workspace and go into Help > Install New Software. I add the ADT Plugin at the URL I then select the Developers Tools and install


With a slow connection,

you could be waiting sometime

I restarted Eclipse and configured the new ADT Plugin to link it to the Android SDK. On launching Eclipse, I’m presented with a Welcome to Android wizard (not used in the instruction at


Using the Eclipse GUI setting up a virtual device is straightforward. I navigate to the correct page on GitHub, download the code and extract as already done twice before and then I import the code as an existing Android project into Eclipse.


On loading the code, that I know should compile, eclipse highlights 2 errors and 13 warnings. As I’m just testing the code today before reviewing it next week. I will ignore the warming but deal with the errors as they prevent me from testing the code. The first error is from the line: import; I download the Gson project from googlecode and add it as an external libray to the project to overcome this. The second error is from the following line: public void onClick(View v). The error is that: The method onClick(View) must override a superclass method so this can be fixed by removing the above @Override annotation


Before I can run the code on the emulator, I create a new andriod project and add the code so far. I then use Run As > Android Application to test the code and it works


I put the android phone into USB debug mode, plug it in and run as. Again it works 🙂

“The best part about being a computer scientist is the feeling of satisfaction when something finally works”

I’m back from brussels

From this …

I arrived in the back in Cambridge yesterday afternoon after the IBM EMEA Best Student Recognition Event 2012 in Brussels, Belgium. The theme of this years 3 day event was “Data Analytics”. The highlight for me on Wednesday 4th July was the a semenar by Prof. Bart Goethals, a lecturer at University Antwerp on data mining and machine learning in data analytics. For Thursday 5th July my highlights were a talk by Corinna Schulze from the IBM Governmental Program on privacy and a talk by Robert-Jan Sips focusing on how data analytics is being applied to water management in the Netherlands.  And for the final day was highlights was a talk by Guy Lefever on the application of Watson to future medical care. Overall I really enjoyed the event and I would throughly recommend attending if you get the opportunity to go.

It looks as if I’m going to have some new work on Signposts next week but I don’t know as yet what this will be so over the weekend I intend to review some of the new material that I’ve learned over the my first few weeks on the Undergraduate Research Opportunities Project (UROP) here at the William Gates Building, Cambridge. My initial project brief was:

Signposts – the virtual personal internet 

Users with multiple networked devices are having a hard time linking them up when said devices reside at more than one location. Simple example is trying to synch your android phone while on the bus to the laptop in your office and the Mac Mini at home. NATs and Firewalls and other obstacles to symmetric communication abound, and obstruct. Point solutions (Dropbox, iCloud) do not deal with many cases (different OS) and only work if you pay (with money or eyeball time on adverts). In any case, they are not acceptable to privacy conscious users.

Instead, we are building a system called signposts. This is the smallest conceivable virtual machine that sits in the public internet, and looks after your personal namespace of devices. Registration and lookup of names is “effectful”, in other words, has side effects. The side effect is to use a set of possible tactics to rendezvous between the devices (various techniques for NAT traversal, for example) including possible multiple simultaneous path use, and also allowing for constraints, such as battery life, and price of use of connections. The system sits on top of DNSSEC, but more interestingly, as a piece of Computer Science, makes use of the new Cloud OS software being developed in CL, called Mirage (see and

This project is to help with the documentation and testing “in the wild” of signposts. We expect to uncover a lot of problems with different oddities (see for examples) that appear, and we need to have good stories to account for what we are doing to the public and to security people. OCaml programming is pretty essential, as well as at least basic understanding of development tools (including git etc) “

Over the last few weeks, I had used a wide range of tools that are new or that I had not previously used to this extent including (in no particular order):

  • Unix command line – although this is something that i typically use, I have definitely used it more and for a wider range of applications that ever before
  • Git & GitHub – for my 2nd year group project PROTON, we took the (controversial) decision to use Mercurial and BitBucket instead of Git and GitHub like most other group so it been interesting to see how they compare
  • Tor – As alot of my work over the last few weeks has been looking at testing the performance of tools for online anonymity, I’ve made extensively use of the onion router
  • Orbot – Tor for android
  • Tails – An OS build around tor
  • Iperf – As just explained as I’ve been working with testing network performance Iperf has been an invaluable tool (though I have recently discovered Torperf)
  • Amazon Elastic Compute Cloud – I’ve been using this a server when testing network performance, its really use as it provides as global domain name and IP address and avoid pathological cases that could be created by having other cleint and server on the same network
  • SHH – for remote access to the other computers I am testing with locally and the virtual machine on Amazon EC2
  • dig-host – command line tools for performing DNS queries, just generally useful
  • CyanogenMod – the OS on my android phone which allows easy using of proxies and tethering
  • Privoxy – heavy customizable non-caching web proxy
  • Hamachi – used with privoxy so set up encrypted VPN access
  • OpenVPN – easy set up of VPNs
  • Texmaker – a nice LaTeX editor, that I would throughly recommend which I have been using to keep the notes on my work over the last few weeks
  • Mozilla Firefox & addons – previously a Chrome user myself, I’ve opted to use Firefox since the research project begin for a change and during this time I have experimented with a range of addons for privacy including: HTTPS Everywhere, NoScript,  AdBlock Plus, DoNotTrackPlus, Collusion …
  • Eclipse & Android Development tools – getting to grips with the basics of Android development in preparation for the Google European Android Camp
  • Telnet – for commend line control of Tor
  • Wireshark – very useful for learning about computer networking, allows you to watch the packets on the network
  • TraceRoute – brillient tools which used TTL to should the route that a packet takes to its destination
  • Ocaml – the main project that I’m working with over the summer makes extensive use of Ocaml

I plan to use this list to visit some of the material that I’ve learned over the last few weeks in preparation for new work next week.