Add guide how to connect to any service hosted at localhost from real device connected through Visual Studio

[janseris]

Description

For MAUI run on Windows, it is easy to access localhost, it's simply localhost.
For MAUI run on Android emulator, simply replace localhost with 10.0.2.2
This is from this guide: https://docs.microsoft.com/en-us/xamarin/cross-platform/deploy-test/connect-to-local-web-services and it works fine.

For SQL Server Express used from emulator there is a nice tutorial here which works (the most important part is to open TCP/IP connections in the server config) (however the new Microsoft.Sql.Data client does not work on Android or works only for newer Android (depending on the version)):
https://www.youtube.com/watch?v=xNmIdFjXzl4

But for Android device which runs MAUI application attached via Visual Studio debugger? 10.0.2.2 doesn't work.

How to please connect to a service hosted on localhost?
Not only HTTP but also TDS or any other protocol.

There is no guide for Android device afaik. But testing must be done also on a real device!

Thank you.

Public API Changes

Add documentation on how to access localhost from Android device when running via Visual Studio (both Debug and Release).

Intended Use-Case

Simulating production environment with MAUI app,

Possible workaround

• to connect localhost to Android device, if these are on the same network, a temporary private IP can be exposed by localhost and ports with applications open. However this is not a robust solution and router can frequently change the private IP addresses assigned to devices (having a static private IP address in a network is not guaranteed)

VS bug #1745020

[Eilon]

@janseris how is the Android device connected to the development machine? Is it via USB, WiFi, or something else? I wonder if this might affect the guidance?

[Eilon]

And I wonder what happens if you use the machine's actual IP address on whatever network it's on. Does that work?

[janseris]

@janseris how is the Android device connected to the development machine? Is it via USB, WiFi, or something else? I wonder if this might affect the guidance?

I am using USB connection to connect the Android device to the Windows host machine.
I saw some options like remote device access through a paid service over the internet but these are probably hard to set up and unrealistic for my or my company's use case.

[janseris]

And I wonder what happens if you use the machine's actual IP address on whatever network it's on. Does that work?

Yes, I have successfully tested accessing the application using the machine's private IP address on the local network.
Configuring a firewall rule for inbound traffic on the correct is enough (and configuring the service to allow TCP connection and communicate on that exact port).

I could use public IP address as well but only if:

• I had access control to the router and could forward the requests to my device
  • possible at home (fullcontrol over the router)
  • not possible at work or at any other network

Problems about using private/local IP address:

• I have to set up a firewall rule on the machine to allow requests to pass through for every application which I want to access
• if the network is large and there are a lot of devices, the private IP can change frequently (in days or hours)
  • because of that, a hardcoded IP address of the server (host machine) service will stop working sooner or later
• the Android device can be using a different network (e.g. mobile data or a different Wi-Fi) than the host machine which it is connected to

Expected behavior:

• a magic IP address like 10.0.2.2 like when using Android emulator which makes the services running at the host machine available to the device connected through USB
  • or over Wi-Fi but that is not needed in my case (but might be in someone else's use case (I am not very familiar with debugging Android apps over direct Wi-Fi connection))

Possible temporal workaround #2:

• using a traffic tunelling service like ngrok with paid plan
  • static dedicated IP address is not available for free
  • pain to set up for anything else than casual HTTP (e.g. gRPC (requires a plain TCP connection for ngrok) or TDS)

[KazysNoobiys]

I use https://github.com/jocull/SharpProxy to connect a real device to a server on the local network.

[mattleibow]

Does 10.0.2.2 still not work in an android app? this should work on any android emulator - regardless of framework. Maybe there was an issue with the runtime and general communication.

Hi @janseris. We have added the "s/needs-info" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 4 days. It will be closed if no further activity occurs within 3 days of this comment. If it is closed, feel free to comment when you are able to provide the additional information and we will re-investigate.

[AlexGoOn]

Does 10.0.2.2 still not work in an android app? this should work on any android emulator - regardless of framework. Maybe there was an issue with the runtime and general communication.

I think the point is that "10.0.2.2" doesn't work when an Android device is used through USB debugging, not when an emulator is used. It seems that I have the same issue.