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 MessengerOptions exist for using the advanced features of Windows Messenger with a non-UPNP firewall. Points to consider on this topic include:
This section will document the basic protocol port usage for the Windows Messenger client used in the Microsoft Live Communications Server enterprise scenario.
Instant MessagingIM and presence are carried over SIP signaling. The SIP signaling can be carried over TCP in clear text or encrypted in a TLS session.TCP Mode Client The clients send and listen on a dynamic port for SIP traffic. The client will send to the server port.
Server 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.
TLS ModeClient 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 SharingThe Whiteboard and Application Sharing components of messenger use the T.120 protocol. The port used is fixed and can not be changed.Protocol PortT.120 1503(TCP)
File TransferThe messenger file transfer protocol uses the TFTP running over TCP.The port range used is fixed and can not be changed.Protocol Ports TFTP 6891 – 6900 (TCP)
Audio and VideoAudio 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 MaxMinSipDynamicPort Specifies the lower port used SIP 7100 1024 65535MaxSipDynamicPort Specifies the highest port used for SIP 7103 1024 65535MinMediaPort Specifies the lower port used for Audio and Video signaling 5350 1024 65535MaxMediaPort Specifies the highest port used for Audio and Video signaling 5353 1024 65535
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