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Port numbers in Visual Studio projects and IIS

I have a few questions about localhost and port numbers as this is an area where I do not have a lot of knowledge, and because I recently had to work with setting up Visual Studio projects and IIS and there are things I'm not clear on.

I have the following questions on the things I find confusing. I thought it made more sense to include them all in one question instead of making separate questions.

  1. I have noticed a random port number is generated with projects I have worked on in the past, but I recently saw a project where the port number was fixed. What is the purpose of having a fixed/default localhost port number? i.e is it particularly useful on projects that have many programmers working on the project?

  2. If a solution contains multiple projects (for example, WCF services, Domain, MVC/Web pages), is it possible to setup a different localhost port for each of them? If so, what is the benefit of this?

  3. If a solution contains multiple projects and has different localhost urls/port numbers, must there be a corresponding website (and application pool) for each project in IIS? Or just for the project that contains the actual web pages?