Microsoft made available for download for Microsoft Developer Network (MSDN) subscribers the promised preview builds of its "Blue" Windows Server and SQL Server releases.

Several MSDN subscribers said on Twitter they were downloading the Windows Server 2012 R2 Datacenter preview, as well as the SQL Server 2014 Community Technology Preview (CTP) 1 bits starting around 9pm this evening (ET).

Microsoft officials disclosed at TechEd North America earlier this month that the company planned to deliver previews of the next versions of Windows Server, SQL Server, Visual Studio, and System Center around June 26. June 26 is the date when Microsoft will also be making the public preview available of its Windows 8.1 (codenamed "Blue") client.

Robert McLaws, a .Net developer and chief technology officer of AdvancedREI, tweeted about the availability of the preview bits earlier this evening.

Programmer Addison Babcock, based in Edmonton, Canada, likewise noted the availability of the Blue server bits on MSDN this evening:

Microsoft is rolling out previews of its upcoming client, server, and tools releases this week in conjunction with its Build 2013 developer conference. Build kicks off on June 26.

Microsoft is expected to share more about its vision and strategies for getting new and existing developers to write "Metro-Style"/Windows Store/Modern apps (take your pick of adjectives) during this week's show.

The final versions of Windows Server 2012 R2, System Center 2012 R2, and Visual Studio 2013 will be out by the end of calendar 2013 , officials confirmed earlier this month. SQL Server 2014 will be out shortly after these two products, officials said. If Microsoft syncs up the arrival of its Blue servers with Windows Blue, which is highly likely, many of these products could be released to manufacturing by August 2013 (according to tipsters).

Windows Server 2012 R2 includes an updated Hyper-V hypervisor , among other new features. SQL Server 2014 includes integrated in-memory database technology, code named "Hekaton."

Update: Sounds like TechNet subscribers are also able to download the Windows Server 2012 R2 preview tonight, too. (Thanks @MGGJim.)

Update No. 2: In addition to the Windows Server 2012 R2 bits, TechNet subscribers also can grab the SQL Server 2014 CTP1 bits and System Center 2012 R2 bits. (Thanks @Windows4Live)