You can find LW's listening port by going tools > options > advanced > firewall config...you'll see the listening port in the top right corner. After changing the listening port number, click Apply > ok to save the change. LW's default port is 6346, there's probably not much chance that your listening port is one of the ones that Comcast blocks

If your connection's ok then you might not need to change ports...LW might be detecting a firewall within your modem/router, an unconfigured software firewall, a firewall associated with where you're trying to connect from (if it's school, work or a condo/appartment complex) etc .

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