CODESAMPLE

Peer-to-Peer - Kotlin

Peer-to-Peer Kotlin

The Peer-to-Peer (P2P) pattern enables direct communication and data exchange between independent entities (peers) without relying on a central server. Each peer acts as both client and server. This Kotlin example uses Kotlin Coroutines and Channels to simulate a simple P2P network. Peers broadcast messages to each other, and each peer listens for incoming messages to process. The implementation employs ReceiveChannel and SendChannel for asynchronous communication and launch for concurrent message handling, aligning with Kotlin’s concurrency model. The use of data classes for message representation illustrates Kotlin’s conciseness and readability.

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*

data class Message(val sender: String, val content: String)

class Peer(val name: String, val peers: MutableList<Peer>) {
    private val incomingMessages = Channel<Message>()

    fun startListening() = CoroutineScope(Dispatchers.Default).launch {
        for (message in incomingMessages) {
            println("$name received: ${message.sender} -> ${message.content}")
        }
    }

    fun sendMessage(content: String) {
        val message = Message(name, content)
        for (peer in peers) {
            if (peer != this) {
                peer.incomingMessages.send(message)
            }
        }
    }

    fun receiveChannel(): ReceiveChannel<Message> = incomingMessages
}

fun main() {
    val peer1 = Peer("Alice", mutableListOf())
    val peer2 = Peer("Bob", mutableListOf())
    val peer3 = Peer("Charlie", mutableListOf())

    peer1.peers.addAll(listOf(peer2, peer3))
    peer2.peers.addAll(listOf(peer1, peer3))
    peer3.peers.addAll(listOf(peer1, peer2))

    val aliceListener = peer1.startListening()
    val bobListener = peer2.startListening()
    val charlieListener = peer3.startListening()

    peer1.sendMessage("Hello, everyone!")
    peer2.sendMessage("Hi Alice!")
    peer3.sendMessage("Greetings from Charlie.")

    Thread.sleep(1000) // Allow time for messages to propagate

    aliceListener.cancel()
    bobListener.cancel()
    charlieListener.cancel()
}