Tuesday, September 9, 2014

What is FTP?

FTP or File Transfer Protocol
"... is a standard network protocol used to transfer computer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and uses separate control and data connections between the client and the server."
wikipedia.org

One reason why this is being replaced by other network protocol is in its exposure of the user password in plain text for a traditional FTP server. SSH and encrypted FTP sessions have replaced almost all new implementations these days.

Which ports are used by this service?
Standard ports used are port 20 (data) and 21 (command) but this may change depending on the server's settings. On the client FTP site, free standard ports higher than number 1023  is used.



This service by the FTP Server can provide active or passive connection and sometimes both. A simplified explanation in Slacksite.org entitled "Active FTP vs. Passive FTP, a Definitive Explanation" is a good read.

Typically, on the FTP server in Passive mode will require connection to several higher standard ports and this allows larger number of connections. In Active mode, limitation on the server is to how many connections can be done over that one port 20.

How to determine if its in Passive more?
After login to FTP server, type
quote PASV

How to establish connection to an FTP server?
Use an FTP client and enter the FTP server's URL. E.g. on Linux, to connect to the FTP server ftp.myserver.com

ftp ftp.myserver.com

-end-


Friday, September 5, 2014

Microsoft's Windows Defender

It was time to uninstall the McAfee antivirus that came pre-installed with the Windows 8 laptop. Just by doing that I noticed that the bubble appear to say that I am no longer protected and to click it. This is when Windows Defender application started, which makes me wonder if its good enough to replace the previous antivirus.

Doing an update to virus and spyware definition version 1.183.1668.0 on 5th Sept 2014. Will continue to run this with Basic membership setting where this means almost anything could be sent to Microsoft.




Tuesday, August 26, 2014

Quick start to Mozilla Firefox OS 1.x

For those of you who were looking for a new smart phone, it might be good to also look at Firefox OS. This is being developed by Mozilla and will be a game changer.

Quick notes:

  1. Initially known as B2G (Boot to Gecko) in the Mozilla Project and initially demonstrated in 2012
  2. Has a Linux based operating system
  3. Target for smart phones, tablets and smart TV.
  4. Among the first adopter was ZTE Open phone
  5. Its has 4 software layers. I.e. Gonk (Linux kernel), Gecko (application services), XUL Runner (Application run-time) and Gaia (User interface system)
  6. Supports HTML5
  7. Website at https://developer.mozilla.org/en-US/Firefox_OS
  8. Apps can be found at the Firefox marketplace.
Current development is at Firefox OS 1.3 (Stable) and Firefox OS 2.1 (Unstable)  and you can try it out via a simulator.

Following are steps to install and run a simulator:
Requirements: Firefox version 30+

Step 1. Install the simulator.

Open Mozilla Firefox web browser and access "App Manager add-ons" by typing in the URL
https://ftp.mozilla.org/pub/mozilla.org/labs/fxos-simulator/

Click "Install Firefox OS 1.3 Simulator (Stable)" or which ever version pleases you.

When the Pop-up appears, Click "Allow" then wait till the download starts (There isn't any indicator onscreen) and when the Software Installation box appears, click "Install Now".

Click "Firefox OS 1.3 Simulator has been installed successfully."

Step 2:  Check installation

To determine if its installed, open Mozilla Firefox web browser and enter URL as
about:addon

You should see "Firefox OS 1.3 Simulator ...."

Step 3: Start up the App Manager

In Mozilla Firefox web browser enter URL as
about:app-manager

At bottom of the  App Manager click "Start Simulator"
The Firefox OS Simulator will appear as a new Firefox Window.


Congratulations...you now have access to the latest Smartphone OS.





Tuesday, July 8, 2014

Howto Turn On Menu and Back Button Lights on Samsung S3

The Samsung S3 is a clever device to conserve energy, but to some users who keep forgetting where is the frequently invisible "Menu" and "Back" buttons, they should have it lit all the time (and off when screen is off).

These buttons are on the left (Menu) and right (Back) of the Home button. By default, each time either keys are pressed, the lights will stay lit for about 1.5 seconds only.


Here are step to have "Menu" and "Back" buttons lit all the time (and off when screen is off).

Step 1. At the Home screen, go to settings.
Simple? For the unacquainted, just touch the Apps button (usually the centre circle at bottom of the screen) and choose settings.

Step 2. Choose "My device", scroll down and touch "Display". 

Step 3. Scroll down to touch "Touch key light duration".

 Step 4. Choose "Always on".

Press "Home" and you will notice the lights are lit next to the "Home" key. If the screen if off, these lights will also go off.

Howto Turn Off Samsung S3 keyboard sound

For some reason, the keyboard on Samsung S3 (GT-I9300) started to beep with each press and this gets annoying after having to type lots. Instructions can be applied for most Android 4, but here the screenshot are for Android 4.3 kernel version 3.0.31-2429075 dpi@HP20 #1.

To turn off/on the sound in 3 simple steps;

Step 1. At the Home screen, go to settings.
Simple? For the unacquainted, just touch the Apps button (usually the centre circle at bottom of the screen) and choose settings.

Step 2. Choose "My device", scroll down and touch "Language and input"





Step 3. Scroll down and find Key-tap feedback "Sound". To turn keyboard sounds off, uncheck the "Sound" box.


Press the "Home" key and you can test out keyboard sound, off or on as you have  selected.


Thursday, May 15, 2014

Writing Equations in Moodle - Part 2

This is a follow up post on enabling users to write equations in Moodle. In the previous post, the required tools were installed on Linux (Centos Linux) and we resume from there.

Step 1:

Login as administrator in Moodle. In the Administration menu, click on Plugins-> Filters-> Manage filters
Choose Filter for Tex notation and change Active? to On. If you click Settings it will bring you to the same screen as in the next step below.

In the Administration menu, click on Plugins-> Filters-> Tex notation
Verify that Path of Latex, dvips and convert binary all contain the linux tools that was created in Part 1 of this tutorial.

Latex = /usr/bin/latex
dvips = /usr/bin/dvips
convert = /usr/bin/convert

Change the convert output format to PNG.

Step 2:

Within a course, create a content and notice that the Insert equation button is visible in TinyMCE editor.

Tuesday, May 6, 2014

OSS Meetup in Kuala Lumpur

Those who are keen to meet fellow OSS in Kuala Lumpur should register for the Malaysia Open Source Community Meetup Q2 2014.

Date: 31 May 2014
Time: 9Am to 2PM
Registration: Required

Please go to the above link for further details.

Writing Equations in Moodle - Part 1

Moodle leverages on MathML for users to enter Math equations. Moodle 2 comes with DragMath and this reduces the need for complicated installation of libraries. On Linux, equations can be displayed with Latex through the use of MimeTex (http://www.ctan.org/tex-archive/support/mimetex) and the newer MathTex.

Examples on the use of MathText can be found at http://www.forkosh.com/mimetex.html#examples

Inserting math equation on a Moodle require certain filters to be enabled but before doing this, the related linux tools need to be installed. End users will need to ensure Java's JRE is installed and enabled in their web browser.

The required Linux (Referring to Centos Linux) tools to be installed include packages mimetex, texlive, texlive-dvips, texlive-latex, ImageMagick and their dependencies. The important tools that should be working and that is needed by Moodle later includes;
/usr/bin/latex
/usr/bin/dvips
/usr/bin/convert

A good tip on enabling Java in web browsers can be found at the Java site. (https://www.java.com/en/download/help/java_blocked.xml)

Tuesday, February 25, 2014

Managing PostgreSQL with pgsql and pgAdmin3

The command line interface (CLI) tool that comes with Postgres server is known as pgsql. Alternatively, pgAdmin3 and phpPgAdmin can be installed.

The pgsql

Among some of the commands for pgsql can be shown as below;





pgAdmin3



Try out SQL statements within these tools. I found one nice reference at http://www.itl.nist.gov/div897/ctg/dm/sql_examples.htm

Installing PostgreSQL on Centos 6

PostgreSQL being an OSS licensed database is very different compared to MySQL. PostgreSQL (or Postges) maintains a repository for Linux systems like Centos to install the database. This repository is known as pgdg and is maintained at yum.postgresql.org or yum.pgrpms.org

Installation of the Postgres comes with psql, this is a CLI to manage Postgres.

Installation of PostgreSQL 9.3 on Centos 6.4 is as follows;

Step 1:
Open a CLI as root user and retrieve the pgdg repo RPM, then install it. This will allow the Centos to find for software from the pgdg.

wget http://yum.postgresql.org/9.3/redhat/rhel-6-x86_64/pgdg-centos93-9.3-1.noarch.rpm
rpm -ivh pgdg-centos93-9.3-1.noarch.rpm

wget http://yum.pgrpms.org/9.3/redhat/rhel-6-x86_64/pgdg-centos93-9.3-1.noarch.rpm
rpm -ivh pgdg-centos93-9.3-1.noarch.rpm

Step 2:
Install the client and server.

yum groupinstall "PostgreSQL Database Server 9.3 PGDG"

yum install postgresql93 postgresql93-server

(-)


Step 3:
Initialise database and tables, and start. This creates the default user postgres.

service postgresql-9.3 initdb
service postgresql-9.3 start

You can now login with the default user to the Postgres terminal as follows;

[root]# su postgres
bash$ cd
bash$ psql -d postgres

If you get the error "psql: could not connect to server: No such file or directory...." Ensure the postgresql server service is running.
Step 4:
As the postgres user, create an administrative user, then log out from the psql (use \q), then the shell (Control-d).

CREATE ROLE dbmsuser LOGIN PASSWORD 'password' SUPERUSER;

As reference, here is summary of the syntax:
CREATE ROLE name [ [WITH] option [ . . . ] ]

 where option includes:
SUPERUSER | NOSUPERUSER
LOGIN | NOLOGIN

Step 5:
Edit Postgres configuration file;

vi /var/lib/pgsql/9.3/data/postgresql.conf

Uncomment the line and save.
#listen_addresses = ‘localhost’ and change it to listen_addresses = ‘*’

vi /var/lib/pgsql/9.3/data/pg_hba.conf

Add a line at bottom of the file to allow non-local connections, e.g.
host    all             dbmsuser        10.0.0.1/32            md5


Post installation
chkconfig postgresql-9.3 on

Ref: