Question

I’m able to access my laptop web server using the Android emulator, I’m using 10.0.2.2:portno
works well.

But when I connect my real Android phone, the phone browser can’t connect to the same web server on my laptop. The phone is connected to the laptop using a USB cable. If I run the
adb devices command, I can see my phone.

What am I missing?

Answer 1

USB doesn’t provide network to mobile device.

If both your desktop and phone are connected to the same WiFi (or any other local network), then use your desktop IP address assigned by the router (not localhost and not 127.0.0.1).

To find out the IP address of your desktop:

• type into the command line ipconfig (Windows) or ifconfig (Unix)
  • on Linux the one-liner ifconfig | grep "inet " | grep -v 127.0.0.1 will yield only the important stuff
  • there’s a bunch of suggestions on how to have a similar output on Windows
• there’s going to be a bunch of IP’s
• try all of them (except the forementioned localhost and 127.0.0.1)

If your phone is connected to the mobile network, then things are going to be harder.

Either go hardcore:

• first find out your router external IP address (https://www.google.de/search?q=myip)
• then, on the router, forward some port to <your desktop IP>:<server port number>
• finally use the external IP address and forwarded port

Otherwise use something like xip.io or ngrok.

NOTE: The ifconfig command has been deprecated and thus missing by default on Debian Linux, starting from Debian stretch. The new and recommended alternative for examining a network configuration on Debian Linux is ip command. For example to use ip command to display a network configuration run the following:

ip address

The above ip command can be abbreviated to:

ip a

If you still prefer to use ifconfig as part of your daily sys admin routine, you can easily install it as part of the net-tools package.

apt-get install net-tools

Reference is here