Microsoft KB Archive/283022

= The Instant Message Polling and Fixed Ports features in Exchange 2000 =

Article ID: 283022

Article Last Modified on 8/28/2007

-

APPLIES TO


 * Microsoft Exchange 2000 Server Standard Edition

-



This article was previously published under Q283022



SUMMARY
Microsoft Exchange 2000 Service Pack 1 (SP1) introduced a new feature for Instant Messaging named &quot;Polling.&quot; Additionally, the Microsoft MSN Messenger Service version 3.5 for the Exchange 2000 Instant Messaging client introduced support for fixed ports. This article describes these features.

Note Microsoft has discontinued support for the polling feature. For additional information about this change in support, click the following article number to view the article in the Microsoft Knowledge Base:

870570 Microsoft no longer supports the polling mode feature for Exchange Instant Messaging



INTRODUCTION
In versions of Exchange 2000 that are earlier than Exchange 2000 Service Pack 1 (SP1), Instant Messaging did not support proxy servers between Instant Messaging clients and their home servers or between Instant Messaging clients and other Instant Messaging clients that log on from outside a network that is secured by a firewall.

When UserA adds UserB to his or her contact list, UserB's Instant Messaging home server is responsible for sending UserA notifications when UserB's status changes. This is done by the Instant Messaging home server opening a new connection to the client by using a port that is higher than or equal to 1024. If a firewall exists between the client and the Instant Messaging home server, the server cannot open a connection to the client, and the client never receives the status change.

When an Instant Messaging client subscribes to a resource, the client provides a callback header that contains the URL for the resource that receives the callback. For example, a client may provide a callback that looks similar to http://192.168.1.17:1234. The server makes a notification request to this URL:port combination. The notification request opens a new connection to the client. These notification requests are delivered through NOTIFY requests.

Instant Messaging contacts who log on to the Instant Messaging Service through a proxy server or by using network address translation (NAT) can send instant messages to other contacts, but may not be able to receive instant messages. Other Instant Messaging contacts who respond to instant messages from these &quot;external&quot; Instant Messaging contacts receive the following error message in the Instant Messaging window:

The following message could not be delivered to all recipients:

In addition to the error message that is generated in the Instant Messaging window of the Instant Messaging contact, the following error message is logged in the Internet Information Service (IIS) protocol log of the server that is running the Instant Messaging Service:

NOTIFY /instmsg/aliases/ - 500

This behavior may occur if the Instant Messaging Service cannot communicate with an Instant Messaging contact who logs on to the Instant Messaging Service through a proxy server or by using NAT. When an Instant Messaging contact logs on by using one of these methods, the Instant Messaging client registers the client's local area network (LAN) Internet Protocol (IP) address and a dynamic Transmission Control Protocol (TCP) port that is higher than 1024. Generally, these IP addresses are either not routable or not resolvable. Therefore, the Instant Messaging Service cannot deliver the message.

Additionally, authentication can only occur if the client can connect directly to the remote Instant Messaging home server instead of the Instant Messaging router. Client authentication between an Instant Messaging router and a home server translates some of the IP address information in such a way that authentication does not occur. If a client tries to authenticate to a home server that is behind a firewall, port 80 is typically open, and traffic is permitted through. However, when the client registers its IP address and port information to a port that is higher than 1024, the server must be able to connect to that client using those addresses. Because most firewalls do not have all ports that are higher than 1024 open, this functionality is lost.

Before the release of Exchange 2000 SP1, remote users could access the network through Remote Access Service (RAS) or Point-to-Point Tunneling Protocol (PPTP). However, Exchange 2000 SP1 and later includes a new feature for Instant Messaging named &quot;Polling.&quot; Additionally, the MSN Messenger Service 3.5 for the Exchange 2000 Instant Messaging client introduced support for fixed ports. This article describes these new features.



Polling
Polling is a new feature that is available in Exchange 2000 SP1. Polling enables the Instant Messaging client to poll an Instant Messaging home server regularly to look for pending notifications. The client tries to keep an open connection to the Instant Messaging home server. These connections have a limited time span or may be severed by firewalls, by proxies, or by hardware routers. The client re-establishes the connection by periodically polling the server.

To use the new polling feature, you must configure both the client and the server.

For additional information about how to configure settings for polling, click the following article number to view the article in the Microsoft Knowledge Base:

326013 White paper - Instant Message Polling and Fixed Port callback delivery

Note Instant Messaging clients that use the polling feature must have direct access to the Instant Messaging home servers. This means that if you currently have a Firewall Topology Module (FTM) configured that prevents external IP addresses from accessing your Instant Messaging home servers, you must modify these settings for polling clients to work.

To use the new polling feature, you must install either the MSN Messenger 3.5 client that is available from the Exchange 2000 SP1 CD or the MSN Messenger 4.6 client. To download the MSN Messenger 4.6 client, visit the following Microsoft Web site:

http://technet.microsoft.com/en-us/exchange/bb288473.aspx

Fixed ports
Fixed ports delivery was a new feature that was originally introduced in the MSN Messenger client for Exchange 2000, version 3.5.0077. Fixed ports enable the client to configure the port number selection. Without fixed ports, the client chooses a random port that is higher than or equal to 1024. The client can choose a single port or a range of ports to use. By using the fixed ports feature, you can select a specific port and configure firewalls to accept these ports from the Instant Messaging servers for notification callbacks.

Note Although the user interface for the Fixed Port(s) option permits you to type value ranges from 1 to 65535, the actual permissible range is 1025 to 65535. If you select port ranges that are lower than 1025, the Instant Messenger client uses random port selection.

To use the new fixed ports feature, you must install either the MSN Messenger 3.5 client that is available from the Exchange 2000 SP1 CD or the MSN Messenger 4.6 client. To download the MSN Messenger 4.6 client, visit the following Microsoft Web site:

http://technet.microsoft.com/en-us/exchange/bb288473.aspx

For additional information about how to configure fixed ports, click the following article number to view the article in the Microsoft Knowledge Base:

326013 White paper - Instant Message Polling and Fixed Port callback delivery

Additional query words: instmsg polling fixed ports IM

Keywords: kbinfo KB283022

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.