How to use the command 'adb reverse' (with examples)

The adb reverse command is a powerful tool typically leveraged by developers to manage socket connections between a host machine and a connected Android device or emulator. It is part of the Android Debug Bridge (ADB), enabling developers to reverse these socket connections, thus allowing the device or emulator to communicate with the host machine through a specified port. This command greatly aids in testing applications by providing seamless communication between development and testing environments.

Use case 1: List all reverse socket connections from emulators and devices

Code:

adb reverse --list

Motivation:

When working with multiple socket connections across various devices or emulators, it becomes essential to have a clear understanding of all currently active reverse socket connections. Using the adb reverse --list command, developers can easily obtain an overview of these connections. This information is critical as it helps in managing and troubleshooting any port-specific communication issues that may arise during app testing and development.

Explanation:

• adb: This stands for Android Debug Bridge, a versatile command-line tool that lets you communicate with a device.
• reverse: This subcommand is used to reverse socket connections.
• --list: An option to display all active reverse socket connections for all connected devices and emulators.

Example Output:

tcp:8081 tcp:8081
tcp:4000 tcp:5000

This output indicates that port 8081 on the device is mapped to port 8081 on the host, and port 4000 on the device is mapped to port 5000 on the host.

Use case 2: Reverse a TCP port from an emulator or device to localhost

Code:

adb reverse tcp:8080 tcp:8080

Motivation:

During the development of network-based applications, developers often need to test how an app on a device communicates with services hosted on their local machine. By using the adb reverse tcp:remote_port tcp:local_port command, developers can forward a port from the device to a port on their localhost. This helps in creating a development environment that closely mirrors the production setup, allowing for realistic testing scenarios.

Explanation:

• adb: The base command for interacting with a connected device.
• reverse: Specifies that the socket connection should be reversed.
• tcp:8080 tcp:8080: Maps TCP port 8080 on the device to TCP port 8080 on the host. The first tcp:8080 refers to the remote device port, while the second tcp:8080 refers to the local host port.

Example Output:

adb: reverse success

This output confirms that the reverse operation was successfully executed and establishes the connection between the defined ports.

Use case 3: Remove a reverse socket connection from an emulator or device

Code:

adb reverse --remove tcp:8080

Motivation:

After completing tests or when no longer needing a specific tunnel, removing an unnecessary socket connection becomes important to avoid unintended port exposure or potential conflicts. Use the adb reverse --remove tcp:remote_port command to clean up and disconnect the reverse socket connection associated with a particular port.

Explanation:

• adb: This command is run through Android Debug Bridge.
• reverse: Indicates an action on reversed connections.
• --remove: An option used to specify that a socket connection should be removed.
• tcp:8080: Identifies the remote port on the device whose reverse connection is to be removed.

Example Output:

adb: reverse removal success

This output confirms the successful removal of the mentioned reverse socket connection.

Use case 4: Remove all reverse socket connections from all emulators and devices

Code:

adb reverse --remove-all

Motivation:

To maintain a clean and efficient development environment, especially when concluding a session or switching projects, it is useful to remove all reverse socket connections. The adb reverse --remove-all command allows developers to quickly and effortlessly clear all active reverse connections, thus streamlining device and port management.

Explanation:

• adb: Facilitates the interaction with the device or emulator.
• reverse: Used to undertake actions on reversals.
• --remove-all: A switch that commands the removal of all existing reversed socket connections between connected devices and the host.

Example Output:

adb: all reverse removals success

This output signals the successful clearance of all reverse socket connections across all connected devices and emulators.

Conclusion:

The adb reverse command serves as an invaluable tool within the Android developer’s toolkit, enabling the establishment, management, and removal of reverse socket connections between devices and a host machine. Whether listing active connections, reversing new port connections, or cleaning up old ones, understanding and utilizing this command efficiently enhances the testing and debugging phase of application development.