Yahoo Messenger can not start -- Ports used by Yahoo! Messenger

Ports used byYahoo! Messenger
Messenger services uses a variety of ports.

Chat & Messenger --->
TCP Port 5050: Client Access only

Insider/Room Lists --->
TCP Port 80: Client Access only

File Transfer --->
TCP Port 80: Server Access.
Your ISP may block this port, as its used for web hosting.
You can change port in Messenger, Preferences, File Transfer.

Voice Chat --->
UDP 5000-5010
TCP 5000-5001: Client Access
If UDP Fails, TCP will be used instead, see below.

WebCam --->
TCP Port 5100: Client Access

Super Webcam --->
TCP Port 5100: Server Access

P2P Instant Messages --->
TCP Port 5101: Server Access
PMs between Buddys may not use the Yahoo! Server, but this is not a requirement.