Why aren't my networked computers able to access localhost from VS2017?

Coming from XAMPP, using the Apache server, I am used to just test my websites in a networked computer by simply typing IPaddress:PortNumber on the address bar of the desired networked computer.

Then while developing with VS2017, I found out that it is not possible by default. While it works fine in the localhost, any networked computer is unable to access the website. What do I need to access to change the settings so that I can expose it to port 8012 rather than 127.0.0.1:8012 ?

I assume that's the problem here.

Solution

I was able to solve this problem by changing the binding values in applicationhost.config

VS2015 onwards, it can be found inside the individual project folder %ProjectFolder%/.vs/config/

In pre-2015 VS, its available in %USER%/Documents/IISExpress/config/

If you are familar with XAMPP, the setting is similar to %XAMPP%/apache/conf/httpd.conf

The difference is that, instead of setting a Listen port number, you have to properly bind the port in IISExpress
By default, port is bound to localhost for the host computer. Say, port 3940 is bound as *:3940:locahost, which makes it only available to the computer running VS.
To make this available to networked computers, you need to change this section as follows:

Change this:

<bindings>
     <binding protocol="http" bindingInformation="*:3940:localhost" />
</bindings>

to:

<bindings>
     <binding protocol="http" bindingInformation="*:3940:*" />
</bindings>

Note: In some cases, bindingInformation="*:3940:" may be used instead of bindingInformation="*:3940:*"

If after all this, it still does not work, then it may be a firewall issue as @Mukesh pointed out in his comment.

Firewall issues can be quickly found out by simply pinging the target device.

If the ping is successful but the port is not allowed, then open the firewall in advanced mode

Open RUN (Windows + R)

Type firewall.cpl

Click on Advanced Settings

Click on Inbound Rules

Create New Rule

Add your desired port to the rule

Port > Specific local ports: 3940 > Allow the connection > Check all (Domain, Private, Public) > Give a name to your rule: ExampleRule > Finish

You can replace 3940 with your desired port number or port range. It is also possible to select all possible ports.

optional: Although nothing really needs to be done in the client computer, you may need to configure your firewall inbound rule to accept all Inbound connections

If it is not a firewall issue, it can be something else entirely. Maybe you're getting a 400 Error page, or a 503 Error. The following SO questions helped me a lot to tackle those problems (although I had to revert the ACL allowance later). I hope this is useful to someone in the future

IIS Express Configuration

Change binding, ACL and Port forwarding

HTTP 400 Bad Request Error

Solution to this ^ is here

503 Service Unavailable Error

Sometimes this is solved by simply creating binding entries in applicationhost.config

Other times, its the duplicate-binding problem. And you need to remove a binding entry during those times. If you are editing applicationhost.config inside the project folder, then it is okay to keep only one site and binding information.

for my particular case, I had to revert this operation netsh http add urlacl url=http://192.168.10.3:3940/ user=everyone with this netsh http delete urlacl url=http://192.168.10.3:3940/ because I kept getting 502 Bad Gateway error when I tried tunneling.

Things to remember:

Please remember to properly restart IISExpress after each change. Normally VS does this by itself. Just double check for any running instances.

Also, always run VS in administrative mode. This usually clears many problems and also allows all sub-processes, such as IISExpress to startup in elevated privilege mode to avoid permission errors.