How can I make IIS handle net.tcp connections?
You need to add net.tcp to the enabled protocols of your site. Go to IIS Manager, right-click on your website, go to 'Manage Web Site' or 'Manage Application', then to 'Advanced Settings...'. There you see 'Enabled Protocols'. It probably says http. Change it to http,net.tcp.
If you want to configure bindings, right-click on your website and go to 'Edit Bindings...'. The default net.tcp binding is 808:*.
If you want to use WCF services hosted by IIS behind net.tcp, you may also want to check whether you have activated the required Windows Features. Go to your Windows Features and check you have activated 'Windows Communication Foundation Non-HTTP Activation' (found under 'Microsoft .NET Framework 3.5.1').
When you activate this feature, you will get some extra Windows Services. If it still doesn't work, check that the Windows Service named 'Net.Tcp Listener Adapter' is running (it should start automatically but sometimes it doesn't and this is the first place I check when one of my net.tcp services stops working).