Flutter Error:Cannot launch without an active device”

Start emulator → then run:

flutter run

list of checking area

Check if a firewall popup is hiding

Very common on Windows:
When you first run adb, Windows Defender Firewall shows a popup behind other windows and ADB waits forever.

Minimize everything, check taskbar for a “Windows Security / Firewall” dialog.

If you see it → click Allow access.

As soon as you allow, the adb start-server command should finish.

If no popup → go ahead with next steps.

NEXT STEP: Check if ADB PORT (5037) is blocked by another app

ADB hangs at start-server when port 5037 is already used.

➡️ Run this command in CMD (as Administrator):

netstat -aon | find "5037"

You will see one of these:

See what process 4872 actually is

In that Administrator cmd, run:

tasklist /FI "PID eq 4872"