Port 80 becomes unavailable due to other processes running on the machine that also use the same port, such as Internet Information Services (IIS) or SQL Server Reporting Services. Hence you might see the error message.
To resolve these errors, you must identify whether a process is using port 80 by running Netstat, and then do one of the following tasks:
- Disable the process that is using port 80, if it is not needed.
- Reconfigure Tableau Server to use a different port, if the process using port 80 is needed.
- Reconfigure your machine to allow both Tableau Server and the other process to use port 80.
See full article here --->Resolving Port 80 Conflicts
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