无法在 Android 上使用 Ktor 原始套接字接收 UDP 数据报

Question

我正在尝试使用 Ktor 和协程接收 UDP 数据报。我创建了一个简单的 android kotlin 应用程序，并设法使用阻塞 java.nio.DatagramChannel 接收数据报，但不使用 Ktor 的套接字。类似的暂停方法也适用于桌面 Kotlin 应用程序。该应用程序在 Android Studio 模拟器（API 30 设备）和 Android 11 手机上进行了测试。

安卓应用程序

添加到AndroidManifest.xml：

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

添加到 build.gradle 中的依赖项：

    implementation 'io.ktor:ktor-network:2.2.4'

MainViewModel.kt：

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import io.ktor.network.selector.*
import io.ktor.network.sockets.*
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import java.nio.ByteBuffer
import java.nio.channels.DatagramChannel
import java.util.concurrent.Executors

class MainViewModel: ViewModel() {
    private val receiverService = Executors.newSingleThreadExecutor()
    private var messageChannel = DatagramChannel.open()
    private val selector = SelectorManager(Dispatchers.IO)
    private val portBlocking = 15100
    private val portSuspend = 15101

    init {
        addCloseable(selector)
        addCloseable(messageChannel)

        receiveBlocking()
        receiveSuspend()
    }

    private fun receiveBlocking() {
        val bindAddress = java.net.InetSocketAddress(portBlocking)
        messageChannel.bind(bindAddress)
        println("--- Blocking receive at ${messageChannel.localAddress} UDP ---")
        receiverService.submit {
            val buf = ByteBuffer.allocate(1000)
            messageChannel.receive(buf)
            println("--- Received blocking $buf ---")
        }
    }

    private fun receiveSuspend() = viewModelScope.launch {
        val localAddress = InetSocketAddress("127.0.0.1", portSuspend)
        val inSocket = aSocket(selector).udp().bind(localAddress) { reuseAddress = true }
        println("--- Suspend receive at ${inSocket.localAddress} UDP ---")
        val datagram = inSocket.receive()
        println("--- Received suspend ${datagram.packet.readText()} ---")
    }
}

工作桌面应用程序

import io.ktor.network.selector.*
import io.ktor.network.sockets.*
import kotlinx.coroutines.*

const val port = 9000

fun main(args: Array<String>) = runBlocking {
    val selectorManager = SelectorManager(Dispatchers.IO)

    receiveSuspend(selectorManager)
}

private suspend fun receiveSuspend(selector: SelectorManager) {
    val localAddress = InetSocketAddress("127.0.0.1", port)
    val inSocket = aSocket(selector).udp().bind(localAddress) { reuseAddress = true }
    println("--- Suspend receive at ${inSocket.localAddress} UDP ---")
    val datagram = inSocket.receive()
    println("--- Received ${datagram.packet.readText()} ---")
}

Answer 1

我遇到了同样的问题。您实际上需要指定发送者的IP地址。如果您不知道，您可以简单地使用“0.0.0.0”（广播接收）。

val inSocket = aSocket(selector).udp().bind(InetSocketAddress("0.0.0.0", port))

参见如何绑定正确的地址和端口进行UDP通信？.