How to implement a VOIP service on the server? [closed] - http

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I know my question is broad, but I have no clue where to start my research.
How can one implement VoIP on a server? I am fairly certain it does not use the http/https protocol. If so, what standard/famous protocols one can use? are there any open-source ones? What are good references to start working on that?

Start by looking at the SIP,RTP and RTCP protocols. I believe they form a minimalistic set of required protocols for VoiP
Some relevant open source projects:
http://www.fsf.org/campaigns/priority-projects/priority-projects/highpriorityprojects#Replaceskype
"There are a number of such programs, such as Ekiga, Twinkle, Coccinella, QuteCom, and Jitsi. Unfortunately, these programs only replace some of Skype's functionality, and only in some situations. WebRTC has a mission to enable rich, high quality, Real-Time Communications (RTC) applications to be developed in the browser via simple Javascript APIs and HTML5. Developers should consider helping free software VoIP and video, chat, and multimedia communications projects."

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Connection between micro controller and external flash [closed]

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I am using an stm32f2xx-series controller in my project. I want to know whether an external flash is connected to the micro-controller or not without doing any read/write operations to the external flash. Is that possible?
If yes, please explain the means to do so.
If it matters, communication between the controller and the external flash is SPI.
Thanks in advance.
I can't think of any way your firmware can detect the presence of an SPI device without talking to it. Reading a status or device identification register is how you typically probe for it.

Is it possible to programatically filter Skype notifications via their API? [closed]

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Suppose my Skype integration wants to filter notifications for a user to messages that contain the string "server down". Is this possible?
Per default Skype for Business (=SfB) can only block URL or attachments as written here. Maybe there exist an 3rd party application which can do that, but I do not think so. Reason: The problem here is that SfB can perform peer2peer connections (see more here). That means if you and your workmade are in the same network and no firewall restricts you both and you both perform a chat together, the chat is done between both of you (without a real server connection; for more infos see the official documentation inside the 2nd link). So a 3rd party software (which might sitting on the server) will not capture that kind of information. So what you might need is a client software on every PC. But what about the mobile clients then? So I do not think that such a software exists or would be possible to build.

Encrypted UDP (DTLS) in Akka [closed]

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I need to create a server-clients application in Scala/Akka for encrypted live video streaming. Since loosing some packets doesn't matter, but speed (latency) is crucial, UDP is much better than TCP.
As far as I know Akka/Scala/Java don't support DTLS. What would be the best framework / library to use for encryption?
Also, I am still deciding between different Akka libraries to build the core of the application. (Akka I/O, Akka Remoting, Spray, Akka Http, Akka Streams). Is it worth waiting for a stable release of Akka Streams?

XMPP or HTTP. Which one scales better? [closed]

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The author of Professional XMPP Programming with JavaScript and jQuery claims that stateless protocols like HTTP are much better to scale, as servers dont have to exchange the state among them, while the author of XMPP The Definitive Guide, claims that XMPP can scale very much better than HTTP.
I'm mind buggled, which of them scales better than the other?
The answer is, as usual, it depends. XMPP may have better scalability properties for some applications, and HTTP for others.
Since no details are provided, I can only provide an answer in the broadest sense possible. The most important factor of scalability, is if you can easily progressively handle more users / transactions / data. Since HTTP is the most popular protocol in the world, and so many people have experience with it, I believe HTTP scales better because there are more resources, knowledge and people available to make that happen.

Is it possible to build peer-to-peer GSM connection using OpenBTS [closed]

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I read about OpenBTS it's really amazing... but I was wondering if we can use it to build phone-to-phone provider-less network.
Any clues or experiments are really appreciated.
One thing to be aware of is that open BTS is 2G/GSM only - i.e. it does not support 3G/UMTS.
This may or may not be important to you depending on what you would like to achieve.
There does appear to be some discussion on adding this functionality in the future (i.e. building an open node b/RNC effectively) but it will be tricky as the authentication mechanism used in 3G requires the network owning the SIM to provide authentication data for even the most basic communication.
GSM follows a strict client-server model. Mobile phones are intended to be clients.
If you would want to build phones with phone-to-phone capability you would need to implement network functionality in the phone. With this, phone-to-phone (theoretically) could be done in an ad-hoc-network model, with one phone running the network part.
I would suspect that one has to look at impacts on the pyhsical/radio layer as well.
Rather unrealistic, IMHO.
May be of interest:
http://terranet.se/history/
So far this company (TerraNet) seem to be only offering sowftware for creating mesh networks over Wifi (I think Wifi is a big disadvantage due to the battery drain. If only we could use GSM), but they seem to share this idea.

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