React Native无法启动iOS/Android模拟器，报SSL23_GET_SERVER_HELLO未知协议错误

Hey there, I’ve run into this exact same SSL-related ADB error when moving my React Native project to a new workstation—total headache at first, but these steps got me back up and running:

1. Reset ADB’s SSL Connection First #

More often than not, this error comes from a wonky ADB connection state. Let’s reset it completely:

• Open your terminal and run these commands one by one:

  adb kill-server
  adb start-server
  adb reconnect offline
  

  This restarts the ADB daemon and forces a fresh connection handshake, which usually fixes the "unknown protocol" mismatch.

2. Disable Proxy Interference #

New computers often have default proxy/VPN settings that mess with ADB’s unencrypted connections. Here’s how to fix it:

• Shut down any active proxy tools, VPNs, or system-wide proxy settings first.
• Then clear proxy environment variables in your terminal temporarily:

  unset HTTP_PROXY
  unset HTTPS_PROXY
  unset http_proxy
  unset https_proxy
  

  If this works, make sure to add adb to your proxy tool’s exclusion list so it doesn’t get blocked again.

3. Check OpenSSL Version & ADB Compatibility #

The error mentions OpenSSL’s s23_clnt.c file, which points to a version mismatch between OpenSSL on your new computer and ADB:

• First, check your OpenSSL version:

  openssl version
  

  If you’re running OpenSSL 3.x, some older ADB builds struggle with its stricter SSL protocols. Try either:
  • Updating ADB to the latest version via Android Studio’s SDK Manager (go to SDK Tools > Android SDK Platform-Tools and hit "Update")
  • Or temporarily force OpenSSL to use a compatible configuration:

    export OPENSSL_CONF=/dev/null
    

    Then restart ADB and try your React Native command again.

4. Verify Device/Emulator Connection #

For physical devices:

• Unplug and re-plug your device, then make sure you tap "Allow USB Debugging" on the device’s popup.
• Run adb devices to confirm your device shows up as device (not unauthorized or offline).

For emulators:

• Close all running emulators, then launch one directly from Android Studio’s AVD Manager before running npm run android.

5. Wipe React Native’s Cache #

Cross-computer project caches can cause weird connection glitches too. Reset it with:

npm start -- --reset-cache

Once the cache is cleared, try launching your iOS or Android project again.

If none of these work, double-check that your new computer has the correct Android SDK environment variables set—make sure ANDROID_HOME is pointing to your SDK folder, and that $ANDROID_HOME/platform-tools is added to your system PATH so ADB is globally accessible.

内容的提问来源于stack exchange，提问作者Muthu Selvan SR