Android ADB Reverse Port Mapping Script: A bash script that automatically sets up reverse port mapping between an Android device/emulator and your local development machine. Useful for mobile app development when you need your Android app to communicate with a locally running development server.

adb_reverse_port.sh

#!/bin/bash

# This script sets up reverse port mapping between an Android device/emulator and the local development machine.
# It is used to allow the Android app to connect to a local development server running on the host machine.
#
# When running the app in development mode on an Android device/emulator, the app tries to connect to
# localhost:$PORT. However, 'localhost' on the device refers to the device itself, not the development
# machine. This script uses ADB (Android Debug Bridge) to set up reverse port mapping so that when the
# app tries to connect to localhost:$PORT on the device, the connection is reversed back to port $PORT
# on the development machine where the actual server is running.
#
# Usage:
# 1. Make sure ADB is installed and in your system PATH
# 2. Connect an Android device via USB or start an emulator
# 3. Run this script: ./adb_reverse_port.sh
# 4. The script will automatically detect connected devices and set up reverse port mapping
#
# Note: If multiple Android devices/emulators are connected, this script will
# prompt you to select which device to use for port mapping. This ensures the
# correct device is configured when working with multiple test devices.

# Port number for reverse mapping between local machine and Android device/emulator
PORT=3000

# Check if adb command exists in path
if ! command -v adb &> /dev/null; then
    echo -e "\033[31mError: 'adb' command not found. Please add Android Debug Bridge (adb) to your system PATH\033[0m"
    exit 1
fi

# Get list of devices and remove header and empty lines
DEVICES=($(adb devices | grep -v "List" | cut -f 1 | grep -v '^$'))
DEVICE_COUNT=${#DEVICES[@]}

if [ $DEVICE_COUNT -eq 0 ]; then
    echo -e "\033[31mNo devices connected!\033[0m"
    exit 1
elif [ $DEVICE_COUNT -eq 1 ]; then
    SELECTED_DEVICE=${DEVICES[0]}
    echo -e "\033[32mAutomatically selected only connected device: $SELECTED_DEVICE\033[0m"
else
    echo -e "\033[33mMultiple devices found. Please select a device:\033[0m"
    for i in "${!DEVICES[@]}"; do
        echo "[$i] ${DEVICES[$i]}"
    done
    
    read -p "Enter the number of the device to use: " DEVICE_INDEX
    
    if [[ ! $DEVICE_INDEX =~ ^[0-9]+$ ]] || [ $DEVICE_INDEX -ge $DEVICE_COUNT ]; then
        echo -e "\033[31mInvalid selection!\033[0m"
        exit 1
    fi
    
    SELECTED_DEVICE=${DEVICES[$DEVICE_INDEX]}
fi

# Show current reverse port mappings
REVERSE_LIST=$(adb -s $SELECTED_DEVICE reverse --list)
echo -e "\033[36mCurrent reverse port mappings for device $SELECTED_DEVICE:\033[0m"
if [ -z "$REVERSE_LIST" ]; then
    echo -e "\033[90mNo existing port mappings\033[0m"
else
    echo "$REVERSE_LIST"
fi
echo ""

# Only set up reverse port mapping if it doesn't already exist
if ! echo "$REVERSE_LIST" | grep -q "tcp:$PORT tcp:$PORT"; then
    echo -e "\033[33mSetting up reverse port mapping for device $SELECTED_DEVICE...\033[0m"
    if adb -s $SELECTED_DEVICE reverse tcp:$PORT tcp:$PORT > /dev/null; then
        echo -e "\033[32mReverse port mapping set up - device $SELECTED_DEVICE will connect to localhost:$PORT\033[0m"
    else
        echo -e "\033[31mFailed to set up port mapping\033[0m"
        exit 1
    fi
else
    echo -e "\033[32mPort mapping already exists for port $PORT\033[0m"
fi