LCS - Windows Messenger port information for IM, File Transfer, Audio and Video
This post is about the ports in use for Windows Messenger and Live Communications Server.
VERY IMPORTANT: only the IM traffic goes through the LCS server, all other traffic is peer to peer.
Firewalls and Windows Messenger
Options exist for using the advanced features of Windows Messenger with a non-UPNP firewall. Points to consider on this topic include:
- Peers on the same side of the firewall can use all of the features of Windows Messenger.
- IM and Presence will work through most firewall configurations.
- Ports can be opened to allow the peer to peer protocol to function via a firewall.
- Port ranges can be set to fixed ranges using group policy.
This section will document the basic protocol port usage for the Windows Messenger client used in the Microsoft Live Communications Server enterprise scenario.
IM and presence are carried over SIP signaling. The SIP signaling can be carried over TCP in clear text or encrypted in a TLS session.
The clients send and listen on a dynamic port for SIP traffic. The client will send to the server port.
The server listens on the default port of 5060(TCP). Server will send notifications to a client’s dynamic port. The dynamic port range can be controlled via policy but the use of TLS is recommended instead.
Client will listen over the same connection that is open to the server.
The server listens on port 5061(TCP) by default. Server will send to client only over the client’s TLS session.
Whiteboard and Application Sharing
The Whiteboard and Application Sharing components of messenger use the T.120 protocol.
The port used is fixed and can not be changed.
The messenger file transfer protocol uses the TFTP running over TCP.
The port range used is fixed and can not be changed.
TFTP 6891 – 6900 (TCP)
Audio and Video
Audio and video each use a pair of UDP ports for a RTP (Real Time Protocol) stream to transmit data and RTCP (Real Time Transport Protocol) to control the session stream. The ports used are dynamic by default but can be controlled via group policy registry settings.
Policies to control port usage:
Policy Description Default Min Max
MinSipDynamicPort Specifies the lower port used SIP 7100 1024 65535
MaxSipDynamicPort Specifies the highest port used for SIP 7103 1024 65535
MinMediaPort Specifies the lower port used for Audio and Video signaling 5350 1024 65535
MaxMediaPort Specifies the highest port used for Audio and Video signaling 5353 1024 65535
Happy Birthday lil sis