Multicasting

From the old issue of PCQuest magazine on video streaming;

Using unicast, video contents can be communicated to a single machine on a network—a peer-to-peer communication. For such communication, you need to specify the exact IP address of the target machine.

With broadcast, content is communicated to all the machines on the network. All machines receive the content even if they don’t intend to. Such content is delivered using broadcast address for a network. For example, the broadcast address for a 192.168.1.0 network is 192.168.1.255.

For video streaming, neither unicast nor broadcast may be suitable. You may not want to stream video to only one machine. You may like more than one machine to receive the video stream so that more users can watch the video. If you opt for broadcast, you may end up wasting network bandwidth by streaming heavy content like video to all machines and hence to users who might not be interested in watching the video.

This is where Multicast comes to the rescue. In multicast, the server streams the content to a particular IP in the range of 224.0.0.0 to 239.255.255.255. This IP does not fall in the range of the prescribed IP addresses for computer networks. Hence, content delivered to this IP is not received by any machine on the network. Only when a machine connects to this IP, will it be able to retrieve the content and more than one machine can connect to a multicast IP simultaneously.

Full article can be found here.

Letting Flex know about the date format

When you need to pass the date other than in the US format in Flex application, you can use the following code;

import mx.controls.DateField;

var d:Date = DateField.stringToDate("30-12-2007","DD-MM-YYYY");

Original source of this entry.

How to checkout single file from SVN

I've been using SVN for a long time and I was in the habit of checking out the whole folder even if I needed a single file. This habit of mine was working well until I had to check out the folder with around 200 files with hundreds of megabytes of data. I then realized what I've been missing. I tried to checkout single file but SVN wouldn't let me do that. From my perspective, it should be simple as checking out the folder, but it was not. There could be some reasonable explanation for this limitation but I needed to checkout the file and quickly finish my job. After spending few mins on the Internet, I found the solution and thought it would be wise to share it. So, here it goes.

1. Right click on the folder in which you would like to check out the file and select 'SVN Checkout...' from the menu.
2. In the Checkout screen, in URL of repository text box, fill the URL to the folder in the repository from which you would like to checkout the file.
3. Select 'Only this item' from the drop down menu from 'Checkout Depth' in the same screen. Click 'OK' button.
4. You can now see SVN overlay icon on the folder. Also, you will notice that the folder is still empty. Let's check out the single file now.
5. Now, right click again on the same folder and select 'TortoiseSVN -> Repo-browser' from the menu.
6. Repository Browser will take you directly to the folder from which you would like to checkout the file and you can see the files on the right hand side of the screen.
7. Right click on the desire file and select 'Update item to revision' from the menu. Click 'OK' on the next screen. Voila, you have successfully checked out single file.
8. If you have some more files (but not all) to checkout, repeat the last step.

Although it takes little time to check out a single or few files from the repository, I think it's worth doing this way rather than checking out the whole folder when the folder it huge in size. What do you think?