Microsoft KB Archive/889937

= Users cannot receive file transfers, audio, or video behind a NAT device in Windows Messenger 5.0 =

Article ID: 889937

Article Last Modified on 5/21/2007

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APPLIES TO


 * Microsoft Office Live Communications Server 2005 Standard Edition
 * Microsoft Office Live Communications Server 2005 Enterprise Edition
 * Microsoft Office Live Communications Server 2003
 * Microsoft Office Communicator 2005
 * Microsoft Windows Messenger 5.0

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SYMPTOMS
In Microsoft Office Live Communications Server 2003, you may experience the following symptoms:
 * A Microsoft Windows Messenger user &quot;User A&quot; can successfully transfer files to, or send audio or video to, another Windows Messenger user &quot;User B.&quot;
 * &quot;User A&quot; cannot receive file transfers, audio, or video from &quot;User B.&quot;



CAUSE
This issue occurs if one of the Windows Messenger users is behind a network address translation (NAT) device. In this scenario, the user who is behind the NAT device receives a private IP address from that device.

When &quot;User A&quot; starts a session, such as a file transfer session, with &quot;User B,&quot; IP address information is sent between computers from &quot;User A&quot; to &quot;User B.&quot; However, if &quot;User A&quot; is behind a NAT device, this IP address information is a private IP address. When &quot;User B&quot; tries to connect to this private IP address to send a file, or to start an audio or video session, &quot;User B&quot; is not successful. Therefore, file transfer traffic, or audio and video traffic, only travels in one direction between these two users.



MORE INFORMATION
If you have a universal plug-and-play (UPnP)–enabled NAT device configured between the Windows Messenger users, all the Windows Messenger features work as you expect.

Note Transfers of audio, video, and data files is peer-to-peer traffic that occurs between computers that are running Windows Messenger. This traffic does not pass through the Live Communications Server computer.

For additional information about Windows Messenger, visit the following Microsoft Web site:

http://www.microsoft.com/windowsxp/using/windowsmessenger/default.mspx

For additional information about how to deploy Live Communications Server 2003, visit the following Microsoft Web site:

http://office.microsoft.com/en-us/FX011526581033.aspx

Additional query words: LCS 2003 RTC chat IM

Keywords: kbnat kbtshoot kbprb KB889937

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