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BT's SDK for do-it-yourself VoIP apps

BT's SDK takes the complexity out of VoIP application development.

Brien Posey

I have never considered myself a developer, but I have written my share of code over the years. Even so, I always thought that coding VoIP applications would be way beyond my skill level. Earlier this summer, I discovered a software development kit (SDK) that changed my mind.

While attending TechEd in Orlando recently, I visited a booth from a company named BT (I think they said this stands for British Telecom). The company has released a very simple SDK that allows developers to tie into the company's VoIP-based services with minimal effort. Complex VoIP functions can often be called using a single line of code.

During TechEd, the company demonstrated a VoIP-based conference call application. The application simply asks for the phone numbers of the parties that you want to connect to the call. Once the phone numbers have been entered, the application calls each number and then connects the calls together. Although there is nothing astounding about this functionality, what is remarkable is that it uses only around a half-dozen lines of code.

Since this isn't exactly a developer's Web site, I'm not going to bore you by walking you through the process of developing a VoIP application. Besides, the process is simple enough that anyone with basic development skills should be able to code a VoIP application within a matter of a few minutes. What I do want to do is explain how BT's SDK can be used.

The BT SDK provides developers with access to six basic functions. The first of these services is the Short Message Service (SMS). This allows applications to transmit SMS text messages.

The next two services are voice calls and conference calls. These services are pretty much self explanatory.

The fourth service offered by the SDK is an authentication service. This allows developers to build user authentication and user management capabilities into an application.

The SDK's fifth capability is the IAM service or "information about me." Essentially, this service provides an easy way for developers to associate unique information with individual users.

The last of the SDK's capabilities is its ability to track a user's location. For now, this capability is extremely limited. The location function works only if the user happens to be located in the U.K. and is using a mobile phone issued by BT. I have been told that the company plans to expand this service over time.

Although VoIP is known for being low cost in nature, nothing in this world is free. BT provides what it calls a "sandbox environment" that you can use as a way of accessing BT's telephony network free of charge during the development process. The sandbox environment allows you to make voice calls, conference calls and so on free of charge, but there are some usage limits in place that prevent the sandbox environment from being used by production applications. For example, the sandbox environment allows you to make up to 10 international calls per day, but each call must be two minutes or less. Here you can find BT's sandbox environment's usage limits.

BT offers a rather unusual pricing structure for production use. Rather than charging a flat monthly fee or charging by the minute, BT uses a credit system. Various services consume a specific number of credits. For example, voice calls consume 10 credits, regardless of duration or whether the call is domestic or international. In contrast, conference calls require 75 credits. You can access the full pricing schedule here.

As you can see, this SDK can be used to create some rather sophisticated applications without your having to know much about software development. You can download the SDK directly from BT's site.

About the author:
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer, he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at www.brienposey.com.

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