Develop Reference

React native Cannot connect to react-devtools using android simulator

I execute the project with react-native run-android and in another terminal, i do:
npm run react-devtools
and it opens the new window of electron that says:
The react native app it will open in a few seconds...
but nothing happens.
I put in the simulator toggle inspector with Ctrl + m and i can see in networks that it makes a request to http://localhost:8097 and the result is it fails to connect and keeps trying with the same result.
The window of electron that is open it says that it wait connections to the port 8097 so i can see is trying to connect but with no results!

You need to run this command in a new terminal adb reverse tcp:8097 tcp:8097

react-devtools v4 is incompatible with react-native
try version 3 instead of version 4:
npm install -d -g react-devtools#3.x, it's worked for me.

The answer by #Unemployed3494 didn't work for me. Instead I killed all running processes belonging to my Mac OS user with this command:
pkill -u username
After doing so, react devtools connected as expected to the simulator.

React Native app: cannot connect to dev server, but the simulator is running - why?

The image describes my current situation properly. Please have a look at it first.
I am running my app on React Native. I have Android simulator on. I give the command to start the app. The app build finishes, but it says that virtual device not found, and in my simulator, if I open the app manually, it says that it cannot connect to Development server. It shows some issues.
Can anyone help?

Try run react-native run-android to connect your app to the emulator

Check USB Debugging is on(mostly running on virtual devices)
Check how you created project(react-native-cli or Expo) and run relevant app run command
Make sure your development server(node.js) is running when you run app. Sometimes it crashes then you have to again run command to run app
If all the step does not solve your issue try to uninstall app from device and run app again. Since react-native is still developing and its wired sometime these tricks works

I was having the same issue in Ubuntu 16.04. In my case the problem was that node packager wasn't running.
To check is packager is running easily you can open the browser and enter
http://localhost:8081/
You must see "React Native packager is running."
If you dont, then you can start packager from console running
react-native start
If you get an error like
" ERROR watch /your/project/path/android/app/build/intermediates/incremental/mergeDebugResources/merged.dir/values-ru ENOSPC"
Then run first
echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
Then run react-native start again and press the letter R twice in the emulator to reload.

Looking at the screenshot, seems like you don't have adb installed because there is a clear 'adb: not found error'.
Luckily Android studio ships with adb and is present in platform-tools under your Android SDK. (generally in /home/your-user-name/Android/Sdk/)
You only need to use it. Create a symbolic link in '/usr/bin/' or '/usr/local/bin/' depending how you'd like to use it.
Run the command:
sudo ln -s ~/Android/Sdk/platform-tools/adb /usr/local/bin/
After this run the app.

Error in meteor install-sdk android on windows 10

I got an issue on meteor JS on my windows 10, I have installed android studio and Java 8 JDK. On my meteor project I tried to build an android by typing meteor install-sdk android, but I got an error of This command is not yet available on Windows. .. Does anyone have an idea about this?

I know this was posted a year ago, but I found a fix recently, just in case anybody gets stuck on this and needs help.
It's from this link: https://github.com/meteor/meteor/issues/4155#issuecomment-384105563
But I'll repost the solution with a few extra changes I had to make by myself.
Basically you need to install Android studio and run it to get the Android SDK, install the Java JDK, and install Cordova. After this you can add the android platform to meteor.
Steps:
Install Android Studio
Run Android Studio once for download, full installation, and accept terms
Update npm with npm i npm
Run npm install cordova -g (-g flag for global install)
Run meteor npm i -g write-file-atomic path-is-inside async-some dezalgo
Run meteor add-platform android
After doing this, you should be able to run meteor run android-device to run on your Android device using a USB cable.
NOTE:
If you are connected to a WiFi network while running meteor run android-device, you might get an error similar to this:
Error detecting IP address for mobile app to connect to:
Found multiple network interfaces with non-internal IPv4 addresses:
'some IP address', 'some IP address'
Please specify the address that the mobile app should connect
to with --mobile-server.
To fix this, modify the command to:
meteor run android-device --mobile-server <ip.of.my.device>
Of course, ensure your PC and Android device are on the same WiFi network.
Go to Settings>About Device>Status to get your current IP Address on your Android device.
The app will now be installed on your phone over the WiFi connection.
(It might take a while though)
Hope this helps.
Cheers.

React Native 'hello world' quick start: "could not connect to development server"

I'm trying to do the react native 'hello world', and I'm using usb debugging on my android.
I ran react-native run-android, then react-native start.
I can view the js file in localhost, but get 'could not connect to development server' message on my phone.
I followed the instructions to run adb reverse tcp:8081 tcp:8081, then realized that command doesn't exist, so I ran adb forward tcp:8081 tcp:8081 instead.
Still no luck. Using react-native#0.22.0, ubuntu 14.04. My phone is nexus 5 on android 6.0.1.
How can I allow my phone to access my localhost?
By the way, it is working over wifi, but I'd like to get it working over usb.

Just another scenario, this error happened to me when I forgot to run react-native start command. I usually follow the steps here when I start new project. The steps in a nutshell are as follows (Android in my case):
Start Android Studio -> AVD Manager -> select your aVD and click Start from action
inside the directory where you want to create your new project, open your command line and run:
$ react-native init <Your new project name/it is also the registration name>
$ cd <the new directory you created>
$ react-native start //This is the step that I forgot
Open a new command prompt and run the following inside the same directory(you just created) to launch the app on your AVD.
$ react-native run-android
If everything is set up correctly, you should see your new app running in your Android emulator shortly.
You'll find in the file index.android.js in the home directory of your project, the last line contians the App registry using the same name you used in the first command above

adb reverse tcp:8081 tcp:8081 Only works for android 5.0 + for running app on devices with android versions lesser than 5.0 hit following command after npm start is done in Terminal (in app directory folder).
curl "http://localhost:8081/index.android.bundle?platform=android" -o "android/app/src/main/assets/index.android.bundle"
now run the app, it will work. Only drawback is that every time you make a change you need to fire the command again and run the app again.

I found the solution :)
I am on ubuntu 16, so, I used command ip addr show which gave me my computer ip address.
I used this ip address and I was able to access localhost on my mobile.
Finally I added the ip address and port no to devsettings of android phone and My app was able to access development server

10 mins ago I had the same problem I guess, and the way I solved this was reading this
https://facebook.github.io/react-native/docs/running-on-device-android.html
and when I did that, I found that I didn't have android-tools-adb installed,
so looking around I found
'No command 'adb' found' error on Ubuntu
which gives me the answer
sudo apt-get install android-tools-adb
and after all this I set
export PATH=${PATH}:~/android-sdk-linux/tools
export PATH=${PATH}:~/android-sdk-linux/platform-tools
then everything works fine, now I can see my app in my Android device.
BTW the option I choose from react native docs was the one that says me
"Using adb reverse
Note that this option is available on devices running Android 5.0+ (API 21).
Have your device connected via USB with debugging enabled (see paragraph above on how to enable USB debugging on your device).
Run adb reverse tcp:8081 tcp:8081
You can use Reload JS and other development options with no extra configuration

I am having seen the same issue, and that's all because the android app don't have this permission:
<uses-permission android:name="android.permission.INTERNET" />

I had a similar problem. I would get this error when trying to get it to run on device. It was working fine on my simulators on my computer.
The problem was when I would do adb devices or react-native run-android I would get "ADB is Not Recognized as an internal or external command".
So my fix was to add the path to adb.exe's parent directory to my Environment Variables and then restart my command prompts. After I did that, adb devices would not throw the "unrecognized internal external blah" and it listed my device. I then ran react-native run-android and on startup no more red screen showing the completely useless error message Error calling AppRegistry.runApplication! :)
So I found ADB was located in my folder:
C:\Users\dell\AppData\Local\Android\sdk\platform-tools\adb.exe
I am on a Windows 10 system. dell is my user name of the computer.
So I went to System Environemnt Variables then found "Path" then clicked "Edit", then clicked "New" and added in "C:\Users\dell\AppData\Local\Android\sdk\platform-tools".

Getting the red screen on real device with react-native

I am using Mac OS X and an Android Phone 4.4.2
When I deploy the sample AwesomeProject app to the phone I get a Red warning screen which says "Unable to download JS bundle. Did you forget to start the development server or connect your device?"
However, I have started the local dev server and connected the phone to the same wifi. Moreover, when I type "adb devices" I can see my device.
Also I added the IP and port of the server under Dev settings.
I found an advice online to type adb reverse tcp:8081 tcp:8081 but my phone is not android 5.0 which is btw minimum required for dab reverse command.
How should I make it start, please help...

Follow this steps carefully.
Note : All commands need to run inside a project only.
Run below command first
npm react-native start
open other window in same project and Run below command
curl "http://localhost:8081/index.android.bundle?platform=android" -o "android/app/src/main/assets/index.android.bundle"
This will create index.android.bundle in assets folder.
Run below command
npm react-native run-android
Now you can get apk in build folder which will work fine.