Windows Messenger Implementation Considerations

This topic describes the settings that .NET Messenger Service uses for TCP ports, voice communications, file transfer, and firewalls.

TCP Ports

The TCP ports need to be configured so that sockets on a port remain open for extended periods of time.

Voice Communications

.NET Messenger Service establishes an outgoing TCP connection from port 6901 for all voice communications.

In the case of computer-to-computer communications, the call recipient also uses TCP port 6901.

All voice traffic also uses User Datagram Protocol (UDP) packets. The user's computer sends and receives UDP packets at port 6901.

File Transfer

Both incoming and outgoing TCP connections use this range of ports: 6891 to 6900. This allows up to 10 simultaneous file transfers per sender. If you open only port 6891, users will be able to do only one file transfer at a time.


To allow users to have a direct connection to instant messaging services through a firewall, instruct them how to:

  • Open outgoing TCP connections to port 1863 on proxy servers.
  • Determine which kind of proxy server their networks use (HTTP, SOCKS4, or SOCKS5) and enter the corresponding details (such as server name and port number) on the Connection tab of the Options dialog box.
  • Make sure that the internal local area network (LAN) has access to the Domain Name System (DNS) servers to resolve the names of external resources.

The following table shows the Sysgen variables for the Windows Messenger.

Sysgen variable Description
SYSGEN_MESSENGER Adds the Windows Messenger service that detects the presence of contacts, and provides text and voice messaging and file transfers by using Hotmail and Communications Service protocols.

See Also

Windows Messenger Overview

 Last updated on Friday, April 09, 2004

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