Microsoft has released an early version of Indigo, a new communications system intended to let Windows programs more easily connect to other software.

The Community Technology Preview, posted on Tuesday, is available to subscribers of the Microsoft Developer Network (MSDN), the company's service for programmers.

In a few weeks, the tool kit will be available to anyone via a free download, company executives said.

Indigo was one of the three "pillars" of Longhorn, the code name for the next version of Windows, expected to debut in 2006. Last summer, Microsoft revamped its delivery plans for Longhorn in order to meet deadlines.

Under the new plan, Indigo, along with Avalon, a new graphics subsystem, and WinFS, a new file system, are being retooled to work with the existing Windows XP and Windows Server 2003 operating systems, in addition to Longhorn.

The goal of Indigo is to simplify the process of building distributed applications, where software components communicate across a network using Web services protocols. For example, the Indigo communications system will allow an application written with Microsoft's .Net tools to share information with a Java application without the need for special code to bridge the two systems.

Indigo will replace the five different programming methods that Microsoft has today for sending messages between two programs in a distributed system, said Ari Bixhorn, the lead product manager for Web services strategy at Microsoft. The software will use a number of the more recent Web services protocols, including WS-Security and WS-Reliable Messaging, he said.

The preview of Indigo also includes a second technology preview of Avalon.

Microsoft intends to release a beta test version of Indigo in the first half of this year, said Bixhorn. The Community Technology Preview includes all the features planned for the first beta.

A second beta for Indigo is planned some time between now and 2006, when Indigo and Avalon are expected to be completed and shipped as part of Longhorn.