AOL’s Message-Blocking Draws Instant Response

In a cat-and-mouse game with potentially huge stakes, America Online apparently changed its instant messaging software Thursday night to block messages from rival services--only to have Microsoft come out with a new version of its software on Friday that gets around the roadblock.

Instant messaging services allow users to exchange chat-style messages with members of a self-selected group of friends or contacts. AOL dominates the field with about 73 million registered users of its two popular systems, AOL Instant Messenger and ICQ.

AOL published some program code of its Instant Messenger software last year to encourage software developers to come up with applications that exploit the program.

Instead, Yahoo and Microsoft used the protocols to come up with similar software that allows their members to communicate with users of AOL’s Instant Messenger, without first signing up with AOL.

Brian Park, senior producer of Yahoo Messenger, Yahoo’s version of instant messaging, said he was using his software at about 10 p.m. Thursday night when he suddenly started getting error messages when connecting with people on AOL’s software.

Microsoft said it received similar complaints Thursday. Its development team went to work to find a solution to the blockade, which it released Friday.

Competing online service Prodigy says it had a similar problem with AOL when it came out with its instant messaging software a couple of months ago.

AOL reportedly asked Prodigy to license AOL’s own instant messaging software and to pay for the ability to send messages to AOL subscribers. AOL could not be reached for comment.