Implementing SSH Communication in Android Apps with Kotlin and Gradle

A Step-by-Step Guide

In today’s interconnected world, mobile applications often need to communicate securely with remote servers or machines. Secure Shell (SSH) protocol provides a reliable and secure way to establish connections and exchange data between devices. In this blog post, we’ll explore how to integrate SSH communication into Android applications using Kotlin and Gradle, along with a practical example.

Why SSH Communication in Android Apps?

SSH is widely used for secure remote access, file transfer, and command execution on remote machines. Integrating SSH communication into Android apps enables developers to:

1. Securely Access Remote Resources: Access files, databases, or services hosted on remote servers securely.
2. Execute Commands Remotely: Run commands on remote machines or IoT devices from within the Android app.
3. Automate Tasks: Automate tasks such as server maintenance, data synchronization, or device management.

Setting Up Dependencies

To enable SSH communication in your Android app, you’ll need to add the necessary dependencies to your project’s build.gradle file:

dependencies {
    implementation 'com.jcraft:jsch:0.1.55'
}

Writing SSH Communication Code in Kotlin

Now, let’s write the Kotlin code to establish an SSH connection from an Android app to another machine:

import com.jcraft.jsch.ChannelExec
import com.jcraft.jsch.JSch
import java.io.ByteArrayOutputStream

class SSHManager {

    fun executeCommand(
        host: String,
        command: String,
        username: String? = null,
        password: String? = null,
        pemFile: String? = null
    ): Pair<String, String> {
        val jsch = JSch()
        if (pemFile != null) {
            jsch.addIdentity(pemFile)
        }

        val session = if (username != null) {
            jsch.getSession(username, host, 22)
        } else {
            jsch.getSession(host)
        }

        if (password != null) {
            session.setPassword(password)
        }
        session.setConfig("StrictHostKeyChecking", "no")
        session.connect()

        val channel = session.openChannel("exec") as ChannelExec
        val outputStream = ByteArrayOutputStream()
        val errorStream = ByteArrayOutputStream()
        channel.outputStream = outputStream
        channel.setErrStream(errorStream)
        channel.setCommand(command)
        channel.connect()

        while (!channel.isClosed) {
            Thread.sleep(1000)
        }

        channel.disconnect()
        session.disconnect()

        return Pair(outputStream.toString(), errorStream.toString())
    }
}

Using the SSHManager in Your Android App

Now, let’s use the SSHManager class to execute an SSH command from within your Android app:

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val sshManager = SSHManager()

        val host = "example.com"
        val command = "ls -l"
        val username = "username"
        val password = "password"
        val pemFile = "/path/to/private_key.pem"

        val (output, error) = sshManager.executeCommand(host, command, username, password)
        // OR
        // val (output, error) = sshManager.executeCommand(host, command, pemFile=pemFile)

        Log.d("SSH Output", output)
        Log.e("SSH Error", error)
    }
}

Conclusion: Enhancing Android Apps with SSH Communication

Integrating SSH communication into Android apps opens up a wide range of possibilities for securely interacting with remote servers or machines. By following the steps outlined in this guide and using the provided example code, you can easily incorporate SSH functionality into your Android applications, enabling seamless communication with remote resources and devices.

Whether you’re building a file management app, a remote control application, or an IoT device management tool, leveraging SSH communication in your Android apps empowers you to deliver robust, secure, and feature-rich experiences to your users. So go ahead, explore the potential of SSH communication, and take your Android app development to the next level!