Description of the Windows Messenger client basic protocol port usage for instant messaging, file transfer, audio, and video

When you use the advanced features of Microsoft Windows Messenger together with a firewall that is not a UPnP firewall, you should consider the following points:

• Peers that are on the same side of the firewall can use all the features of Windows Messenger.
• Instant messaging (IM) and presence information work through most firewall configurations.
• Ports can be opened to enable the peer-to-peer protocol to function through a firewall.
• Port ranges can be set to fixed ranges by using Group Policy.

Important Only the IM traffic goes through the server that is running Microsoft Office Live Communications Server 2005. All other traffic goes through a peer-to-peer network.

This article introduces the basic protocol port usage for the Windows Messenger client that is used in the Microsoft Office Live Communications Server 2005 Enterprise Edition scenarios and in the Microsoft Office Communicator 2005 scenarios.

IM and presence information

IM and presence information are carried over Session Initiation Protocol (SIP) signaling. The SIP signaling can be carried over Transmission Control Protocol (TCP) in clear text. Or, the SIP signaling can be encrypted in a Transport Layer Security (TLS) session.

TCP mode

Client

The client listens on a dynamic port for SIP traffic. The client sends data to the default port of the server. The default port of the server is 5060.

Server

The server listens on the default port 5060 (TCP). The server sends notifications to a dynamic port of the client. The dynamic port range can be controlled by using Group Policy. However, we recommend that you use TLS instead of TCP.

TLS mode

The client listens over the same connection that is open to the server.

By default, the server listens on port 5061 (TCP). The server will send to the client only over the client's TLS session.

Whiteboard and Application Sharing

The Whiteboard and Application Sharing components of Windows Messenger use the T.120 protocol. The port that is used is fixed and cannot be changed.

File transfer

The messenger file transfer protocol uses the Trivial File Transfer Protocol (TFTP) that is running over TCP. The port range is fixed and cannot be changed.

Audio and video

Audio uses a pair of User Datagram Protocol (UDP) ports for a Real-time Protocol (RTP) stream to transmit data. Video uses Real-time Transport Protocol (RTCP) to control the session stream.

By default, the ports that are used are dynamic. However, the ports can be controlled through Group Policy registry settings. These registry settings are under the following registry key:You can use the following policies to control the port usage.
Important The following settings do not work in Office Communicator. These settings are listed in the Comunicator.ADM file, but they do not work.