Develop Reference

Android Studio error: cannot connect to daemon

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:
Daemon not running. Starting it now on port 5037
Android ADB - Daemon still not running
How to resolve the "ADB server didn't ACK" error?
Eclipse error "ADB server didn't ACK, failed to start daemon"
Adb won't start
How to resolve the "ADB server didn't ACK" error?
Daemon not running. starting it now on port 5037 * Cannot open 'nul': The system cannot find the file specified
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

The solution which worked for me -
Open Command Prompt as administrator and type
adb start-server
That's it

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

Usually that's caused by the WinNAT service, restarting which solves the issue.
Just open the Command Prompt or PowerShell as Administrator, and type the following commands there:
net stop winnat
net start winnat
And wait a bit for the Android Studio to reconnect to the ADB.
P.S. If it doesn't reconnect, just type the following commands to restart the ADB:
adb kill-server
adb start-server

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)

Run CMD or PowerShell as administrator
Then run the following commands:
net stop winnat
In correct folder run:
adb start-server
net stop winnat

Below solution solved my problem:
Go to your task manager
see if adb is running
right click & end the task
Go to command prompt
run adb devices
it will work fine

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.

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

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.

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.

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.

Had same issue after upgrading to Android Studio Bumblebee | 2021.1.1
To solve it, go to Settings -> Build, Excecution, Deployment -> Debugger
Then uncheck the option Enable adb mDNS for wierless debugger

I had the same error.
Error on android studio
i use easytether, which was causing the error when is connected.
http://www.mobile-stream.com/easytether/android_faq.html#adbmacosx
After u disconnect it, everything should work fine.

ADB server not running

When I run ADB and type in "adb start-server" it says
*daemon not running. starting it now on port 5037 *
could not read ok from ADB Server, error = 109
*failed to start daemon *
error: cannot connect to daemon
what should I do? I've tried killing the server and restarting the pc but nothing seems to work. my pc recognizes the phone and the adb process only appears briefly when i try to start the server. also, it gets stuck on wating for device when i type "fastboot oem unlock"

Looks like windows is messing up the ports (reserving them). I have the same issue with docker containers and this worked for me:
Run this in the command line (as administrator)
net stop winnat
adb.exe start-server
net start winnat

Happened with me as well. Just check there might be an existing adb process running in your task manager. Just kill the process and run the 'adb start-server' command.
Hope it helps

Happened to me today.
I realized it happened when I started Android Studio after having my Genymotion emulator running, so I fixed it by closing everything (even check task manager for a running instance of adb).
After closing everything, I opened Android Studio first and then the emulator and everything was ok.

In my case the issue was in IntelliJ IDEA plugin - Aladdin Logcat. Turned it off and everything works now.

This happened to me because I had Oculus Developer Hub open.
Even if you're not using its adb features, it will constantly try to start its own version of adb and kill the one you're trying to launch.

ADB server can't start android

I have installed adt bundle eclipse. However, I can't seems to run the AVD. I have the problem of
ADB server didn't ACK
failed to start daemon
I have search on how to solve it, I've read to type adb kill-server and adb start-server. when I typed that, it says
adb server is out of date. killing...
ADB server didn't ACK
* failed to start daemon *"

Please follow below steps:-
Go to run
open command prompt
get into your platform-tools under android sdk.
now type command: adb kill-server
then upon success type: adb start-server
Thats'it.
Let me know if you still facing any issue..

I had this exact problem on my Vista x64 system. I solved it by doing the following:
Ctrl-Alt-Del, start Task Manager, under Processes tab, check for "shuame_helper.exe". It was there from running RootGenius. I clicked End Process, then went back to the command prompt and entered adb start-server and it worked!

Try below step from DDMS in eclipse :

So I had the same problem and failed in all the same ways as above:
adb kill-server
followed by
adb start-server
still resulted in the ADB server didn't ACK error.
The other common suggestion of using the task manager to kill the process also
failed as it seemed that something restarted adb automatically? It would disappear for a second, then there were two adb processes ,then there was one again.
Exasperated.
I restarted Windows in safe mode.
This ensured that adb wasn't started.
Shut down and restart normally. Problem solved.
Just for good measure, I also updated eclipse and android at this point, but I think that the safe mode restart fixed it.
Give it a try when all else fails.

When this happens I open Activity Monitor (on mac) or Task Manager (on windows) and look for the ADB process and force close it (sometimes there are more than one, close those to) and then press the Run button again in Android Studio or Eclipse.

1)Open task manager first
2)close any instance of adb.exe(end task it)
3)open command prompt
4) type adb start-server(you may have to execute it twice)
5) try to run now.

I had this problem using the latest ADT, SDK and Eclipse on Windows 7. I had an old ASUS TF101 and an HTC HD connected with their respective docking software. When I looked in processor tab of the Windows task manager I could see two instances of the adb.exe, one loaded and another one looking like it is trying to load.
I killed the PC connecting software (process in task manager) for the ASUS, the HTC Sync wasn't running. There is now one adb.exe running and both devices are recognised in Eclipse and in the command prompt (adb devices). You may need to restart Eclipse.

How to resolve the "ADB server didn't ACK" error? [duplicate]

This question already has answers here:
Eclipse error "ADB server didn't ACK, failed to start daemon"
(23 answers)
Adb won't start
(21 answers)
Closed 6 years ago.
I am trying to install my project on 5 AVD's at the same time, but I constantly get this error, I am executing it on Windows 8.1
"* daemon not running. starting it now on port 5037 *
ADB server didn't ACK
* failed to start daemon *
error: cannot connect to daemon"
I have tried reading all possible posts on stackoverflow concerning this error, and all of them just mention that try to kill the adb process and restart eclipse and then all will be fine. I have tried the method mentioned in the posts and along with that I have also turned off my security and firewall, so that there is no obstruction on the port 5037. Somebody please help me as I need to execute my project and I am not able to do so :(. For your reference I can provide the output of the following command "netstat -ano | findstr "5037""
TCP 127.0.0.1:5037 0.0.0.0:0 LISTENING 7144
TCP 127.0.0.1:5037 127.0.0.1:57410 ESTABLISHED 7144
TCP 127.0.0.1:5037 127.0.0.1:57411 ESTABLISHED 7144
TCP 127.0.0.1:5037 127.0.0.1:57414 ESTABLISHED 7144
TCP 127.0.0.1:5037 127.0.0.1:57415 ESTABLISHED 7144
...
Somebody please suggest a workaround this problem, what might be the cause of this. Also you can take a look at the following image to infer what might be happening.

Try the following:
Close Eclipse.
Restart your phone.
End adb.exe process in Task Manager (Windows). In Mac, force close in Activity Monitor.
Issue kill and start command in <sdk_folder>\platform-tools\
C:\sdk\platform-tools>adb kill-server
C:\sdk\platform-tools>adb start-server
If it says something like 'started successfully', you are good.

For anyone using OSX (I'm aware OP isn't):
What worked for me in the end was removing the android settings folder in the home directory.
rm -Rf ~/.android

For me it didn't work , it was related to a path problem happened after android studio 2.0 preview 1, I needed to update genymotion and virtual box, and apparently they tried to use same port for adb.
Solution is explained here link!
Basically you just need to:
1) open genymotion settings
2) specify sdk path for the adb manually
3) adb kill-server
4) adb start-server

Similar questions are
"The connection to adb is down, and a severe error has occured."
The connection to adb is down, and a severe error has occured.You must restart adb and Eclipse.Please ensure that adb is correctly located
ECLIPSE-The connection to adb is down, and a severe error has occured
First close IDE.
In my case I killed adb via Task Manager(adb kill-server did not work)
then adb start-server
daemon not running. starting it now on port 5037 *
daemon started successfully *
If you see "started successfully" than it is solved, now start IDE.

On my Mac, I wrote this code in my Terminal:
xxx-MacBook-Pro:~ xxx$ cd
/Users/xxx/Documents/0_Software/adt20140702/sdk/platform-tools/
xxx-MacBook-Pro:platform-tools xxx$ ./adb kill-server
xxx-MacBook-Pro:platform-tools xxx$ ./adb start-server
daemon not running. starting it now on port 5037 *
daemon started successfully *
xxx-MacBook-Pro:platform-tools tuananh$
Hope this help.

if you are using any mobile suit like mobogenie or something that might also will make this issue. try killing that too from the task manager.
Note : i faced the same issue, tried the above solution. That didn't work, finally found out this solution.May useful for someone else!..

On my end, I used Resource Monitor to see which application was still listening to port 5037 after all the Eclipse and adb restart were unsuccessful for me.
Start > All Programs > Accessories > System Tools >
Resource Monitor > Network > Listening Ports
This eventually showed that java.exe was listening to port 5037, hence, preventing adb from doing so. I killed java.exe, immediately start adb (with adb start-server) and received a confirmation that adb was able to start:
android-sdks\platform-tools>adb start-server
* daemon not running. starting it now on port 5037 *
* daemon started successfully *

I've got a kind of botch for the old ADB server didn't ACK * failed to start daemon * issue which might help, though i haven't seen anyone else with my problem so maybe not. Anyway...
I changed the default install location for my HTC sensation to 2 (SD card), but when trying to revert back to 0 (internal) i was getting this error. Looking in task manager showed there were 2 instances of adb.exe running, one of which kept stopping and starting and was impossible to kill, the other could be killed but then a new instance would start almost immediately.
The only way i could get adb to start successfully was to get my command ready in the command window, go to task manager to end the adb.exe, then when the window came up saying 'are you sure you want to kill adb.exe' dragged that over the command window, clicked OK then immediately pressed Enter to run the command. It seems that the short window between adb.exe being killed and restarting itself is sufficient to run a command, though if you try to do something else it won't work and you have to repeat this process each time you want to run a command.
PITA but it's the only way an uneducated numpty like myself could get round it - hopefully it'll help someone...

i have solve this problem several times using the same steps :
1- Close Eclipse.
2- Restart your phone.
3- End adb.exe process in Task Manager (Windows). In Mac, force close in Activity Monitor.
4- Issue kill and start command in \platform-tools\
C:\sdk\platform-tools>adb kill-server
C:\sdk\platform-tools>adb start-server
5- If it says something like 'started successfully', you are good.
but now it's doesn't work cause i have an anti-virus called "Baidu", this program have run "Baidu ADB server", finally i turn this process off and retry above steps it's work properly.

Eclipse error "ADB server didn't ACK, failed to start daemon"

After updating the SDK, Eclipse shows this error:
ADB server didn't ACK, failed to start daemon.
When I run an Android application, it gives me the following:
Please ensure that adb is correctly located at 'D:\android-sdk-windows\platform-tools\adb.exe' and can be executed.
How can I fix this problem?

Thanks, #jowett, I have solved my same problem, doing these steps
Step 1:
CTRL+Shift+Esc to open the task manager, which has adb.exe process and end (kill) that process
Step 2:
Now, close the eclipse, which is currently running on my computer.
Step 3:
Again, restart eclipse then solved that problem.
For those using OS X
killall adb
For those using Windows
adb kill-server
should do the trick.

I met same problem, though I didn't what caused this. Whatever, i find some clues and fixed finally.
When I open SDK and AVD manager, but find the AVD version(2.3.3) is not same with android lib version(2.3). So I create a new AVD with 2.3.
I fixed it by the following steps:
1. Open windows task manager and kill adb.exe process.
2. Close eclipse and restart it. Then it works.
Hope it helps.

Command prompt (cmd.exe):
netstat -aon | findstr 5037
Find the process id of 0.0.0.0:
Make sure it's adb.exe:
tasklist | findstr 1980
Kill this process:
taskkill /f /t /im adb.exe
Get ADB back to normal:
Credit: blog post *Android ADB server didn't ACK failed to start daemon*

These symptoms occur if you are using the Genymotion emulator (on Windows or Linux) at the same time as Android Studio:
adb server is out of date. killing...
ADB server didn't ACK
* failed to start daemon *
Genymotion includes its own copy of adb, which interferes with the one bundled in the Android SDK.
The easiest way to fix seems to be to update your Genymotion Settings so it uses the same ADB as your Android SDK:
Just check the "Use custom Android SDK tools" option and enter your desired location.

ADB will often fail if there is a newline in adb_usb.ini. Remove it, restart it, and that will often solve the problem (at least for me anyway).

If you are using a sync application for the device, it could also be because there are other apps using the same 5037 port. Shut down all services running on port 5037 and try starting ADB.
To check if any application is using port 5037, use this:
netstat -a -n -o |findstr "5037"
Get the PID of the application.
Use Process Explorer to find the Process and exit it.
Now use adb start-server or adb get-state to start/check the ADB server status.
I faced the issue when I used the Snappea / Wandoujia Sync application.

I caused this problem by entering an extra blank line at the end of ~/.android/adb_usb.ini
(Removing the extra blank line fixed the problem)

We can solve this issue so easily.
Open a command prompt, and do cd <platform-tools directory>
Run command adb kill-server
Open Windows Task manager and check whether adb is still running. If it is, just kill adb.exe
Run command adb start-server in the command prompt

I have solved my first question: Open Eclipse, open the SDK Manager, and choose the device to open.
Or you can open the SDK directory. Open the SDK Manager, and then choose the device to open
2: Close Eclipse, and then open it.

Make sure USB debugging on your phone is turned on. ADB kill-server and ADB start-server is not the problem.
C:\Documents and Settings\Administrator> adb nodaemon server
- cannot bind 'tcp:5037'
C:\Documents and Settings\Administrator> netstat -aon | findstr "5037"
- TCP 127.0.0.1:1130 127.0.0.1:5037 TIME_WAIT 0
- TCP 127.0.0.1:1269 127.0.0.1:5037 TIME_WAIT 0
- TCP 127.0.0.1:5037 0.0.0.0:0 LISTENING 3088
- TCP 127.0.0.1:5037 127.0.0.1:1128 TIME_WAIT 0
- TCP 127.0.0.1:5037 127.0.0.1:1129 TIME_WAIT 0
- TCP 127.0.0.1:5037 127.0.0.1:1270 TIME_WAIT 0
C:\Documents and Settings\Administrator>tasklist -fi "pid eq 3088"
- Image name PID session name session # memory usage
========================= ====== ================ ======== ============
- adb.exe 3088 Console 0 3,816 K
C:\Documents and Settings\Administrator>taskkill /f /pid 3088
- Success: terminate the PID for the process of 3,088.
C:\Documents and Settings\Administrator>adb start-server
- daemon not running. starting it now on port 5037 *
- daemon started successfully *

I've already up-voted another answer here to this question, but just in case anyone was wondering, you don't need to restart Eclipse to get ADB running again. Just open a shell and run the command:
adb start-server
If you haven't set the path to ADB in your system properties then you must first go to the directory in which ADB exists(in Android\android-sdk\platform-tools....I'm running Windows, I don't know how the mac people do things).

Run over to sysinternals.com and pick up TCPVIEW and PROCESS EXPLORER, if you don't have them installed already.
For some reason, the ADB daemon is terminating before the close socket exchange is complete. If you run (from the command prompt) "NETSTAT -o", you will see the socket (generally 5037) in CLOSE_WAIT state and the owning process number. Process Explorer won't show that process ID (the daemon terminated), and the process called adb.exe (which opened the socket) will be gone. (If adb.exe if found, try killing the task and see if things get cleaned up.)
Using TCPVIEW, locate the hung socket. The process name column will show the associated process can not be found. Right click, and select "Close Connection". The socket is now closed, and the adb daemon should be able to start.

I had a similar issue. Killing an existing instance of the ADB process from Task Manager did not work for me.
Just few days back, I had tried to install MIPS SDK and ADT-17 earlier and Eclipse gave me the error, and I did not fix that issue.
So, now, when I got this ADB server didn't ACK, failed to start daemon... issue, I executed 'Check for Updates' in the Eclipse Help menu item.
There were no updates available, but at least 'ADB server did not ACK' error disappeared.
I hope this might help in a few cases.

Type ./adb nodaemon server in a terminal.
If it returns Invalid content in adb_usb.ini, then there is a problem with your adb_usb.ini file in the .android folder.
Open adb_usb.ini and erase its contents. Then restart the server...it worked for me.

Check for the path of the Android directory. It should not contain spaces, etc.
Also check if the plugin has been properly configured in Eclipse → Preferences.
In my case I had everything checked multiple times, but it was still not working. I was about to reinstall everything, but I came upon an answer on this site (some other post).
Do check your antivirus. It may be blocking the ports of adb.exe or emulator programs, etc. That solved the problem in my case.

In addition to #Bastet's solution:
Actually we have to kill the process using the address 0.0.0.0:0. That's why for most of the people killing adb.exe from Task Manager was working (in my case I was not able to see it even in Task Manager).
Following the #Bastet steps, I found out that some other process was using this address. I went ahead to kill it, and it gave me ACCESS DENIED as Error.
So using the tasklist | findstr **** I found out the name of the process and killed it from Task Manager.
Thereafter it started working.
In my case bas_daemon and bas_helper were using this address both of which corresponds to MOBOROBO.

I had the same problem. But there was no process of adb on my laptop. I just log out and log in to my account, and it's resolved...
ADB could start from CMD windows after that.

The best and the most efficient way without restarting any device or software is:
Run the following:
adt-bundle-windows-x86_64\sdk\platform-tools\adb.exe
And one more thing.. ADB is a self-dependent thing. You cannot do anything until unless it wants itself to work. There is one more way which I found out: Leave the device connected for 5-6 minutes and wait. Soon the device gets connected and tries to launch.

This didn't start happening for me until I rooted my Samsung Galaxy S III phone (following the xda-developer forum guide).
It happens pretty randomly, but it's definitely occurring while running Eclipse.
Killing the adb.exe process and restarting it solves the problem.

Look at the antivirus or firewall... Does any of that block you from access... In k7 antivirus I turned off system monitor, and it does works for me...

Linux/Ubuntu users this might also be the case.... i had an android emulator running and I had to kill that. To do that do the following
lsof -i :5307
(use sudo if needed)
Note the pid in the result of above command. Then
kill -9 <pid_from_above>
then go ahead with
adb shell

I had to allow adb.exe to access my network in my firewall.

Killing Eclipse and then rebooting did not help me. I added the Android tool to the PATH variables, started Task Manager and killed adb.exe.
I restarted Eclipse, and then it worked.