Android Studio error: cannot connect to daemon

Question

I've been using AS for months, but since two days I get an error when I try to run my app:

Unable to run 'adb': null
'C:\Users\lapof\AppData\Local\Android\Sdk\platform-tools\adb.exe start-server' failed -- run manually if necessary
* daemon not running; starting now at tcp:5037
could not read ok from ADB Server
* failed to start daemon
error: cannot connect to daemon

I've read about a lot of people having this problem, but the solutions provided don't work for me. I read these questions in particular:

A lot of answers to these questions say to close adb.exe from task manager, the problem is that adb.exe is not running and if I try to restart it by typing .\adb start-server on a PowerShell window I get the same error.

I also try to restart my PC but it didn't work. On the Android device I'm trying to connect to (Samsung Galaxy S8) I enabled USB debugging. I even tried to eliminate all the authorized devices, but nothing worked.

I checked if the 5037 port was used by other processes, but it is used by adb.exe (and the firewall state on that port is allowed and not limited). By the way, as I said, in the task manager adb.exe is not present.

Last I tried to follow the instructions provided in the last question I linked (basically I re-downloaded adb.exe). Initially I ran .\adb start-server and this strange error occurs:

* daemon not running. starting it now on port 5037 *
* daemon started successfully *
** daemon still not running
error: cannot connect to daemon

and then when I try to run my app on Android Studio it occurs this new error when it tries to start adb:

Unable to run 'adb': null
'C:\Users\lapof\AppData\Local\Android\Sdk\platform-tools\adb.exe start-server' failed -- run manually if necessary
ADB server didn't ACK
* failed to start daemon *

and then if I try to .\adb kill-server and then .\adb start-server or .\adb devices or .\adb usb the same error occurs again. Moreover when I connect my device now it asks me to authorize my PC to connect.

I don't know if this can help, but lately I deactivated a lot of Windows services (but I don't think I deactivated something related to Android Studio).

Details

PC: Compaq
PC OS: Windows 10 Home
Device: Samsung Galaxy S8 (Exynos)
Device OS: Android 8.0
AS version: 3.0.1

I'd suspect it to already run, possibly due to having Genemotion installed `stop-server` & `start-server` ordinary helps; also make sure no local firewall is blocking the default port `tcp:5555`. — Martin Zeitler, Sep 04 '18 at 20:54
`Start > All Programs > Accessories > System Tools > Resource Monitor > Network > Listening Ports` can be used to see if the port is already in used by any other application. — Martin Zeitler, Sep 04 '18 at 20:56
@MartinZeitler I don't use Genymotion (my old PC doesn't support emulators :( ). Why is port 5555 important? Isn't adb using 5037? — Lapo, Sep 04 '18 at 20:56
@MartinZeitler Yes, I used that exact same path to find out that 5037 port is used by adb.exe. Port 5555 is not in that list tho. Thanks — Lapo, Sep 04 '18 at 20:57
https://developer.android.com/studio/command-line/adb#howadbworks ...it's always a pair of ports, 1 per adb device and 1 per adb server ...eg. two hardware devices would require 4 ports (no matter if automatically assigned or explicitly passed). — Martin Zeitler, Sep 04 '18 at 21:00
@MartinZeitler ok thanks, btw port 5555 is not in the list of Listened Ports. Is this an issue? — Lapo, Sep 04 '18 at 21:04

score 13 · Answer 1 · answered Jan 03 '20 at 14:08

13

The solution which worked for me -

Open Command Prompt as administrator and type

adb start-server

That's it

answered Jan 03 '20 at 14:08

Payel Senapati

469
3
12

We should restart AS after this? – MMG Aug 13 '20 at 10:59

canmustu · Answer 2 · 2021-05-18T23:58:19.143

11

I had same problem a moment ago. I solved it:

Run CMD as Administrator

Enter adb devices to CMD.

The output for me is :

C:\WINDOWS\system32>adb devices
List of devices attached
* daemon not running; starting now at tcp:5037
* daemon started successfully
P9BCS87ABS9SCD5 device

edited May 18 '21 at 23:58

answered Dec 27 '18 at 23:35

canmustu

1,426
2
16
28

1

'adb' is not recognized as an internal or external command, operable program or batch file. How to deal this – Kusumakar Pant Jul 09 '19 at 21:51
@KusumakarPant Either you add adb to the path or you use the full path – yoel halb Oct 11 '19 at 16:00
Thanks, this solved it, note that as soon as the daemon is started it will already work even from a non admin console – yoel halb Oct 11 '19 at 16:01
that was an interesting trick ;) mine was version doesn't match error. It killed and started after this command – Prabs Nov 13 '19 at 07:09

score 4 · Accepted Answer · answered Sep 05 '18 at 12:23

I solved the problem on my own.

Out of frustration I opened Control Panel > System and security > Windows defender firewall > Allowed applications and I added adb.exe (both private and public networks).

I came back to Android Studio, ran the app and magically it managed to initialize ADB and my phone connected via USB was there.

I don't really know why this worked, since when I checked in Start > All Programs > Accessories > System Tools > Resource Monitor > Network > Listening Port it said that on port 5037 the firewall was allowed.

Moreover I don't know why up to a week ago all worked fine and now I had to do this process to make it work.

If someone more experienced manages to explain this behaviour better I'll update this answer (or accepts his as best answer)

score 3 · Answer 4 · answered Jul 15 '20 at 02:56

For my situation The latest platform is version 30.0.3. I also have the same problem as this:

* daemon not running. starting it now on port 5037 *
* daemon started successfully *

My solving:

Step 1: downloading platform-tool version 28.0.1: https://developer.android.com/studio/releases/platform-tools#2801_september_2018
Step 2: remove platform-tool: go to SDK Manager -> SDK tools Uncheck "Android SDK Platform - Tool" Click Apply
Step 3: Going to folder android -> SDK and pass new platform-tool
Step 4: ADB devices. Then It's working for me.

score 2 · Answer 5 · answered Mar 20 '19 at 05:04

2

SDK Manager -> SDK tools
Uncheck "Android SDK Platform - Tool"
Click Apply

answered Mar 20 '19 at 05:04

Miler Roque

39
2

This just removed adb for me. This is not a solution to follow. After reinstallation, the connection did work however. – Akaisteph7 May 23 '19 at 21:10
Thanks, this was the only solution that worked for me (after reinstalling) – souzan Nov 21 '19 at 07:22

score 2 · Answer 6 · answered Dec 02 '19 at 02:47

After using Android Studio and Emulator without any problems, suddenly it stop to connect to the Emulator, even adb server was running (killing and starting), firewalls raised for all the programs (adb.exe, qemu-system-x86_64.exe, studio64.exe, etc), port 5037 freed, uninstalled and installed again the programs, even the whole Android Studio from scratch. I got verything running OK, but no connection between AS and Emulator.

The solution to my problem was to run Android Studio AS ADMINISTRATOR, it seems that when I updated the program to 3.5.2 somehow the status changed, causing me the problem.

Hope this help anyone out there like me that passed several days trying all what is written on Internet to fix the issue.

When I got the problem over an year ago, I haven't tried this! Probably a very good solution. Luckily it hasn't happened to me again. — Lapo, Dec 02 '19 at 22:18

score 0 · Answer 7 · answered Aug 13 '20 at 11:10

I had this issue several times. It seems if when system is starting, device is connected by USB cable, daemon will connect correctly and no problem will occur. Of course I want a better solution, because it is very hard for me to shut down and start again every time.

score 0 · Answer 8 · answered Apr 14 '21 at 23:04

0

What worked for me in all adb unresolved cases:

adb kill-server

or

adb disconnect

I would just try them both and one will do the trick.

answered Apr 14 '21 at 23:04

Gogu CelMare

455
3
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Android Studio error: cannot connect to daemon

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