Comcast currently blocks ports 25, 68, 135-139, 445, 520, and 1080.
It is questionable whether some of these ports are presently blocked.
See this topic: Blocked ports
Also, see this Comcast FAQ link.
*This FAQ is based on user knowledge from a volunteer core of BroadbandReports' members. This FAQ in no way constitutes official information from Comcast or any of its affiliates.
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