refactor basic

WIP

.gitignore

@@ -46,3 +46,4 @@ bin/
 
 .idea/
 /src/nativeInterop/cinterop/def/
+/src/cinterop/win32_join_multicast_group.def

README.md

@@ -7,6 +7,7 @@ Also, nmdns can be compiled to shared/static lib for other languages calling, se
 mDNS is usually used for Apple's AirPlay protocol family, there's an example in README.md [How to use](#How-to-use)
 
 Supported platforms:
+
 1. windows64(mingwx64)
 2. linuxX64
 3. linuxArm64
@@ -14,13 +15,25 @@ Supported platforms:
 5. macosX64
 6. jvm(11 or later)
 
+
+Platform implementations are based on:
+
+- Apple: posix socket
+- Windows: WinSock
+- Linux: posix socket
+- JVM: `java.net.MulticastSocket`
+
+No external dependencies required.
+
 Supported record type
+
 1. A
 2. PTR
 3. SRV
 4. TXT
 
 Supported features
+
 1. Event hooking(Kotlin only)
 
 > AAAA is not supported

build.gradle.kts

@@ -2,9 +2,10 @@ import com.vanniktech.maven.publish.SonatypeHost
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
-    kotlin("multiplatform") version "2.2.0"
+    kotlin("multiplatform") version "2.3.10"
     id("com.vanniktech.maven.publish") version "0.31.0-rc2"
     id("signing")
+    id("cn.rtast.kdef") version "0.1.1"
 }
 
 val libVersion: String by project
@@ -20,7 +21,14 @@ kotlin {
     val nativeTargets = listOf(
         linuxArm64(),
         linuxX64(),
-        mingwX64(),
+        mingwX64 {
+            compilations["main"].cinterops {
+                @Suppress("UNUSED")
+                val joinMulticastGroup by creating {
+                    definitionFile = file("src/cinterop/win32_join_multicast_group.def")
+                }
+            }
+        },
         macosArm64(),
         macosX64()
     )
@@ -126,3 +134,8 @@ tasks.register("linkSharedLibrary") {
     dependsOn(tasks.named("linkReleaseSharedMacosArm64"))
     dependsOn(tasks.named("linkReleaseSharedMingwX64"))
 }
+
+kdef {
+    outputDir = file("src/cinterop")
+    defFiles.add(file("src/cinterop/template/win32_join_multicast_group.def"))
+}

clibs/win32_join_multicast.c

@@ -0,0 +1,40 @@
+#include "win32_join_multicast.h"
+
+#include <stdint.h>
+#include <winsock2.h>
+#include <ws2tcpip.h>
+
+int join_multicast_group(SOCKET sock, const char *group) {
+    struct ip_mreq mreq;
+    mreq.imr_multiaddr.s_addr = inet_addr(group);
+    mreq.imr_interface.s_addr = INADDR_ANY;
+
+    if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *) &mreq, sizeof(mreq)) == SOCKET_ERROR) {
+        return 1;
+    }
+    return 0;
+}
+
+int socket_sendto(SOCKET fd, const uint8_t *data, int len, const char *host, unsigned short port) {
+    struct sockaddr_in addr;
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(port);
+    addr.sin_addr.s_addr = inet_addr(host);
+
+    const int sent = sendto(fd, (const char *) data, len, 0, (struct sockaddr *) &addr, sizeof(addr));
+    if (sent == SOCKET_ERROR) {
+        return 1;
+    }
+    return 0;
+}
+
+int leave_multicast_group(SOCKET sock, const char *group) {
+    struct ip_mreq mreq;
+    mreq.imr_multiaddr.s_addr = inet_addr(group);
+    mreq.imr_interface.s_addr = INADDR_ANY;
+
+    if (setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char *) &mreq, sizeof(mreq)) == SOCKET_ERROR) {
+        return 1;
+    }
+    return 0;
+}

clibs/win32_join_multicast.h

@@ -0,0 +1,22 @@
+#ifndef WIN32_JOIN_MULTICAST_H
+#define WIN32_JOIN_MULTICAST_H
+
+#include <stdint.h>
+#include <winsock2.h>
+
+#ifdef __cplusplus
+extern "C" {
+
+#endif
+
+int join_multicast_group(SOCKET sock, const char *group);
+
+int socket_sendto(SOCKET fd, const uint8_t *data, int len, const char *host, unsigned short port);
+
+int leave_multicast_group(SOCKET sock, const char *group);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // WIN32_JOIN_MULTICAST_H

src/appleMain/kotlin/cn/rtast/nmdns/socket.apple.kt

@@ -1,69 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-
-@file:OptIn(ExperimentalForeignApi::class)
-@file:Suppress("unused")
-
-package cn.rtast.nmdns
-
-import kotlinx.cinterop.*
-import platform.darwin.inet_addr
-import platform.posix.*
-
-public actual class Socket1 internal actual constructor() {
-    /**
-     * socket fd
-     */
-    private var socket: Int = -1
-
-    public actual fun bind(ip: String, port: Int): Socket1 {
-        socket = socket(AF_INET, SOCK_DGRAM, 0)
-        if (socket < 0) perror("Failed to create udp socket")
-        memScoped {
-            val reuse = alloc<IntVar>()
-            reuse.value = 1
-            if (setsockopt(socket, SOL_SOCKET, SO_REUSEADDR, reuse.ptr, sizeOf<IntVar>().convert()) < 0) {
-                perror("Failed to setsocketopt SO_REUSEADDR")
-            }
-        }
-        memScoped {
-            val addr = alloc<sockaddr_in>()
-            addr.sin_family = AF_INET.convert()
-            addr.sin_port = htons(port.toUShort())
-            addr.sin_addr.s_addr = inet_addr(ip)
-            if (bind(socket, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert()) < 0) {
-                perror("Failed to bind")
-                close(socket)
-            }
-        }
-        memScoped {
-            val mreq = alloc<ip_mreq>()
-            mreq.imr_multiaddr.s_addr = inet_addr("224.0.0.251")
-            mreq.imr_interface.s_addr = inet_addr(ip)
-            if (setsockopt(socket, IPPROTO_IP, IP_ADD_MEMBERSHIP, mreq.ptr, sizeOf<ip_mreq>().convert()) < 0) {
-                perror("setsockopt IP_ADD_MEMBERSHIP")
-            }
-        }
-
-        return this
-    }
-
-    public actual fun send(packet: ByteArray) {
-        memScoped {
-            val addr = alloc<sockaddr_in>()
-            addr.sin_family = AF_INET.convert()
-            addr.sin_port = htons(5353u)
-            addr.sin_addr.s_addr = inet_addr("224.0.0.251")
-            val cbuf = packet.refTo(0).getPointer(this)
-            sendto(socket, cbuf, packet.size.convert(), 0, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert())
-        }
-    }
-
-    public actual fun destroy() {
-        close(socket)
-    }
-}

src/appleMain/kotlin/cn/rtast/nmdns/util/multicast_socket.apple.kt

@@ -0,0 +1,60 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+@file:OptIn(ExperimentalForeignApi::class)
+
+package cn.rtast.nmdns.util
+
+import kotlinx.cinterop.*
+import platform.darwin.inet_addr
+import platform.darwin.sockaddr_in
+import platform.posix.*
+
+public actual class MulticastSocket actual constructor() {
+
+    private var fd: Int = -1
+
+    public actual fun bind(port: Int): Unit = memScoped {
+        fd = socket(AF_INET, SOCK_DGRAM, 0)
+        val opt = alloc<IntVar>()
+        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, opt.ptr, sizeOf<IntVar>().convert())
+        val addr = alloc<sockaddr_in>()
+        addr.sin_family = AF_INET.convert()
+        addr.sin_port = htons(port.toUShort())
+        addr.sin_addr.s_addr = INADDR_ANY
+        bind(fd, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert())
+    }
+
+    public actual fun joinMulticastGroup(group: String): Unit = memScoped {
+        val merq = alloc<ip_mreq>()
+        merq.imr_multiaddr.s_addr = inet_addr(group)
+        merq.imr_interface.s_addr = INADDR_ANY
+        setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, merq.ptr, sizeOf<ip_mreq>().convert())
+    }
+
+    public actual fun send(data: ByteArray, host: String, port: Int): Unit = memScoped {
+        val addr = alloc<sockaddr_in>()
+        addr.sin_family = AF_INET.convert()
+        addr.sin_port = htons(port.toUShort())
+        addr.sin_addr.s_addr = inet_addr(host)
+        data.usePinned {
+            sendto(fd, it.addressOf(0), data.size.convert(), 0, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert())
+        }
+    }
+
+    public actual fun receive(buf: ByteArray): Long = memScoped {
+        buf.usePinned { recv(fd, it.addressOf(0), buf.size.convert(), 0) }
+    }
+
+    public actual fun close(): Unit = run { if (fd > 0) close(fd) }
+
+    public actual fun leaveMulticastGroup(group: String): Unit = memScoped {
+        val merq = alloc<ip_mreq>()
+        merq.imr_multiaddr.s_addr = inet_addr(group)
+        merq.imr_interface.s_addr = INADDR_ANY
+        setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, merq.ptr, sizeOf<ip_mreq>().convert())
+    }
+}

src/appleTest/kotlin/test/TestApple.kt

@@ -7,7 +7,7 @@
 
 package test
 
-import cn.rtast.nmdns.randomMacAddress
+import cn.rtast.nmdns.util.randomMacAddress
 import cn.rtast.nmdns.registerService
 import cn.rtast.nmdns.sleep1
 import kotlin.test.Test

src/cinterop/template/win32_join_multicast_group.def

@@ -0,0 +1,3 @@
+headers = {{PATH}}/clibs/win32_join_multicast.h
+compilerOpts = -I{{PATH}}/clibs
+linkerOpts = {{PATH}}/src/cinterop/libwin32_join_multicast_group.a -lws2_32

src/commonMain/kotlin/cn/rtast/nmdns/CExport.kt

@@ -1,13 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-
-package cn.rtast.nmdns
-
-@Target(AnnotationTarget.FUNCTION)
-@Retention(AnnotationRetention.BINARY)
-@RequiresOptIn
-public annotation class CExport

src/commonMain/kotlin/cn/rtast/nmdns/MDNSRecord.kt

@@ -0,0 +1,16 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/14
+ */
+
+
+package cn.rtast.nmdns
+
+public data class MDNSRecord(
+    val name: String,
+    val type: String,
+    val host: String,
+    val port: Int,
+    val txt: Map<String, String> = emptyMap(),
+)

src/commonMain/kotlin/cn/rtast/nmdns/mdns_announcer.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/14
+ */
+
+
+package cn.rtast.nmdns
+
+import cn.rtast.nmdns.util.MulticastSocket
+
+public class MDNSAnnouncer(private val socket: MulticastSocket) {
+
+    public fun register(record: MDNSRecord) {
+
+    }
+
+    public fun unregister(record: MDNSRecord) {
+
+    }
+
+    public fun onQuery(callback: (queryType: String, queryName: String) -> Unit) {}
+
+    public fun start() {
+
+    }
+
+
+    public fun stop() {
+
+    }
+}

src/commonMain/kotlin/cn/rtast/nmdns/nmdns_announcer.kt

@@ -1,247 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/28/25
- */
-
-
-@file:OptIn(ExperimentalNativeApi::class)
-
-package cn.rtast.nmdns
-
-import kotlin.experimental.ExperimentalNativeApi
-import kotlin.native.CName
-
-public fun NMDNSAnnouncer.onRegister(callback: () -> Unit) {
-    onRegisterCallback = callback
-}
-
-public fun NMDNSAnnouncer.onBroadcast(callback: () -> Unit) {
-    onBroadcastCallback = callback
-}
-
-public fun NMDNSAnnouncer.onUnregistered(callback: () -> Unit) {
-    onUnregisterCallback = callback
-}
-
-public data class NMDNSAnnouncer(
-    /**
-     * service type
-     * airplay service type: _airplay._tcp.local.
-     */
-    internal val serviceType: String,
-    /**
-     * service name
-     */
-    internal val serviceName: String,
-    /**
-     * local hostname
-     */
-    internal val hostname: String,
-    /**
-     * service ip, lan ip mostly
-     */
-    internal val ipAddress: String,
-    /**
-     * service port
-     */
-    internal val port: Int = 7004,
-    /**
-     * mdns server port
-     */
-    internal val mdnsPort: Int = 3025,
-    /**
-     * txt record content
-     */
-    internal val txtRecords: List<String>,
-    /**
-     * mdns socket server
-     */
-    internal val server: Socket1,
-    /**
-     * srv packet
-     */
-    internal val packet: ByteArray,
-) {
-
-    internal var onRegisterCallback: (() -> Unit)? = null
-    internal var onBroadcastCallback: (() -> Unit)? = null
-    internal var onUnregisterCallback: (() -> Unit)? = null
-
-    override fun equals(other: Any?): Boolean {
-        if (this === other) return true
-        if (other == null || this::class != other::class) return false
-
-        other as NMDNSAnnouncer
-
-        if (port != other.port) return false
-        if (mdnsPort != other.mdnsPort) return false
-        if (serviceType != other.serviceType) return false
-        if (serviceName != other.serviceName) return false
-        if (hostname != other.hostname) return false
-        if (ipAddress != other.ipAddress) return false
-        if (txtRecords != other.txtRecords) return false
-        if (server != other.server) return false
-        if (!packet.contentEquals(other.packet)) return false
-
-        return true
-    }
-
-    override fun hashCode(): Int {
-        var result = port
-        result = 31 * result + mdnsPort
-        result = 31 * result + serviceType.hashCode()
-        result = 31 * result + serviceName.hashCode()
-        result = 31 * result + hostname.hashCode()
-        result = 31 * result + ipAddress.hashCode()
-        result = 31 * result + txtRecords.hashCode()
-        result = 31 * result + server.hashCode()
-        result = 31 * result + packet.contentHashCode()
-        return result
-    }
-
-    /**
-     * broadcast packet
-     */
-    public fun broadcast() {
-        this.onBroadcastCallback?.invoke()
-        this.server.send(packet)
-    }
-
-    /**
-     * unregister service
-     */
-    public fun unregister() {
-        this.onUnregisterCallback?.invoke()
-        this.server.destroy()
-    }
-}
-
-/**
- * broadcast packet
- * export for c
- */
-@CExport
-@CName("broadcast")
-public fun broadcast1(server: NMDNSAnnouncer) {
-    server.server.send(server.packet)
-}
-
-/**
- * unregister service
- * export for c
- */
-@CExport
-@CName("unregister")
-public fun unregister1(server: NMDNSAnnouncer) {
-    server.unregister()
-}
-
-/**
- * register service
- * airplay2 txt records
- * listOf(
- *     "deviceid=${randomMacAddress()}",
- *     "model=AppleTV3,2C",
- *     "features=0x5A7FFFF7,0x1E",
- *     "srcvers=220.68",
- *     "pk=f3769a660475d27b4f6040381d784645e13e21c53e6d2da6a8c3d757086fc336"
- * )
- */
-@CName("register_service")
-public fun registerService(
-    serviceType: String,
-    serviceName: String,
-    hostname: String,
-    ipAddress: String,
-    port: Int,
-    mdnsPort: Int = 9872,
-    bindAddress: String,
-    txtRecords: List<String>,
-    callback: NMDNSAnnouncer.() -> Unit = {},
-): NMDNSAnnouncer {
-    val socket = createSocket()
-        .bind(bindAddress, mdnsPort)
-
-    val server = NMDNSAnnouncer(
-        serviceType,
-        serviceName,
-        hostname,
-        ipAddress,
-        port,
-        mdnsPort,
-        txtRecords,
-        socket,
-        buildPacket(serviceType, "$serviceName.$serviceType", hostname, ipAddress, port, txtRecords),
-    )
-    server.callback()
-    server.onRegisterCallback?.invoke()
-    return server
-}
-
-internal fun buildPacket(
-    serviceType: String,
-    serviceName: String,
-    hostname: String,
-    ip: String,
-    port: Int,
-    txtRecords: List<String>,
-): ByteArray {
-    val records = mutableListOf<ByteArray>()
-    records += encodeRR(serviceType, 12, encodeName(serviceName))
-
-    val srvData = ByteArray(6) { 0 }
-    srvData[4] = (port shr 8).toByte()
-    srvData[5] = (port and 0xFF).toByte()
-    records += encodeRR(serviceName, 33, srvData + encodeName(hostname))
-
-    val ipParts = ip.split(".").map { it.toInt().toByte() }
-    records += encodeRR(hostname, 1, ipParts.toByteArray())
-
-    if (txtRecords.isNotEmpty()) {
-        val txtData = encodeTxt(txtRecords)
-        records += encodeRR(serviceName, 16, txtData)
-    }
-
-    val header = ByteArray(12)
-    header[2] = 0x84.toByte()
-    header[3] = 0x00
-
-    header[6] = ((records.size shr 8) and 0xFF).toByte()
-    header[7] = (records.size and 0xFF).toByte()
-
-    return header + records.reduce { acc, r -> acc + r }
-}
-
-internal fun encodeRR(name: String, type: Int, data: ByteArray): ByteArray {
-    val nameBytes = encodeName(name)
-    val rr = ByteArray(10)
-    rr[0] = 0x00; rr[1] = type.toByte()
-    rr[2] = 0x00; rr[3] = 0x01
-    rr[4] = 0x00; rr[5] = 0x00; rr[6] = 0x00; rr[7] = 0x78
-    rr[8] = (data.size shr 8).toByte()
-    rr[9] = (data.size and 0xFF).toByte()
-    return nameBytes + rr + data
-}
-
-internal fun encodeName(name: String): ByteArray {
-    val parts = name.trimEnd('.').split(".")
-    val bytes = mutableListOf<Byte>()
-    for (p in parts) {
-        bytes += p.length.toByte()
-        bytes += p.encodeToByteArray().toList()
-    }
-    bytes += 0
-    return bytes.toByteArray()
-}
-
-internal fun encodeTxt(records: List<String>): ByteArray {
-    val bytes = mutableListOf<Byte>()
-    for (txt in records) {
-        val txtBytes = txt.encodeToByteArray()
-        if (txtBytes.size > 255) continue
-        bytes += txtBytes.size.toByte()
-        bytes += txtBytes.toList()
-    }
-    return bytes.toByteArray()
-}

src/commonMain/kotlin/cn/rtast/nmdns/sleep1.kt

@@ -1,15 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/29/25
- */
-
-
-package cn.rtast.nmdns
-
-/**
- * block current thread
- * unit: second
- */
-
-public expect fun sleep1(time: Int)

src/commonMain/kotlin/cn/rtast/nmdns/socket.kt

@@ -1,38 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-@file:Suppress("unused")
-
-
-package cn.rtast.nmdns
-
-public expect class Socket1 internal constructor() {
-    /**
-     * bind to ip
-     */
-    public fun bind(ip: String, port: Int): Socket1
-
-    /**
-     * send packet
-     */
-    public fun send(packet: ByteArray)
-
-    /**
-     * close
-     */
-    public fun destroy()
-}
-
-internal fun createSocket(): Socket1 = Socket1()
-
-public fun htons(value: UShort): UShort =
-    (((value.toInt() and 0xFF) shl 8) or ((value.toInt() ushr 8) and 0xFF)).toUShort()
-
-public fun htonl(value: UInt): UInt =
-    ((value and 0xFFu) shl 24) or
-            ((value and 0xFF00u) shl 8) or
-            ((value and 0xFF0000u) shr 8) or
-            ((value and 0xFF000000u) shr 24)

src/commonMain/kotlin/cn/rtast/nmdns/util/byte_util.kt

@@ -0,0 +1,12 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+package cn.rtast.nmdns.util
+
+
+public fun htons(value: UShort): UShort =
+    (((value.toInt() and 0xFF) shl 8) or ((value.toInt() ushr 8) and 0xFF)).toUShort()

src/commonMain/kotlin/cn/rtast/nmdns/util/bytearray_builder.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+package cn.rtast.nmdns.util
+
+internal class ByteArrayBuilder {
+    private val buffer = mutableListOf<Byte>()
+
+    fun appendByte(b: Int) = apply { buffer.add(b.toByte()) }
+
+    fun appendShort(value: Int) = apply {
+        buffer.add(((value shr 8) and 0xFF).toByte())
+        buffer.add((value and 0xFF).toByte())
+    }
+
+    fun appendInt(value: Int) = apply {
+        buffer.add(((value shr 24) and 0xFF).toByte())
+        buffer.add(((value shr 16) and 0xFF).toByte())
+        buffer.add(((value shr 8) and 0xFF).toByte())
+        buffer.add((value and 0xFF).toByte())
+    }
+
+    fun appendBytes(bytes: ByteArray) = apply { buffer.addAll(bytes.toList()) }
+
+    fun appendName(name: String): ByteArrayBuilder {
+        val labels = name.split(".")
+        for (label in labels) {
+            appendByte(label.length)
+            appendBytes(label.encodeToByteArray())
+        }
+        appendByte(0)
+        return this
+    }
+
+    fun build(): ByteArray = buffer.toByteArray()
+}
+
+internal fun dnsPacket(block: ByteArrayBuilder.() -> Unit) =
+    ByteArrayBuilder().apply(block).build()

src/commonMain/kotlin/cn/rtast/nmdns/util/mac.kt

@@ -5,17 +5,15 @@
  */
 
 
-package cn.rtast.nmdns
+package cn.rtast.nmdns.util
 
 import kotlin.experimental.ExperimentalNativeApi
-import kotlin.native.CName
 import kotlin.random.Random
 
 /**
  * generate random mac address
  */
 @OptIn(ExperimentalNativeApi::class)
-@CName("random_mac_address")
 public fun randomMacAddress(): String {
     val bytes = ByteArray(6) { Random.nextInt(0, 256).toByte() }
     return bytes.joinToString(":") { it.toHexString() }

src/commonMain/kotlin/cn/rtast/nmdns/util/mdns_packet.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+package cn.rtast.nmdns.util
+
+internal fun buildMDNSResponse(
+    host: String,
+    service: String,
+    ip: String,
+    port: Int,
+    txtRecords: Map<String, String>,
+): ByteArray = dnsPacket {
+    // HEADER
+    appendShort(0); appendShort(0x8400)
+    appendShort(0); appendShort(4)
+    appendShort(0); appendShort(0)
+
+    // PTR
+    appendName("_airplay._tcp.local"); appendShort(12)
+    appendShort(0x8001); appendInt(4500)
+    val ptr = dnsPacket ptr@{ this@ptr.appendName(service) }
+    appendShort(ptr.size); appendBytes(ptr)
+
+    // SRV
+    appendName(service); appendShort(33)
+    appendShort(0x8001); appendInt(120);
+    appendShort(0); appendShort(0)
+    appendShort(port)
+    val srv = dnsPacket srv@{ this@srv.appendName(host) }
+    appendShort(srv.size); appendBytes(srv)
+
+    // TXT
+    appendName(service); appendShort(16)
+    appendShort(0x8001); appendInt(4500)
+    val txt = dnsPacket txt@{
+        for ((k, v) in txtRecords) {
+            val entry = "$k=$v".encodeToByteArray()
+            this@txt.appendByte(entry.size); this@txt.appendBytes(entry)
+        }
+    }
+    appendShort(txt.size); appendBytes(txt)
+
+    // A
+    appendName(host); appendShort(1)
+    appendShort(0x8001); appendInt(120)
+    val ipParts = ip.split(".").map { it.toInt() and 0xff }
+    appendShort(4); appendByte(ipParts[0]); appendByte(ipParts[1])
+    appendByte(ipParts[2]); appendByte(ipParts[3])
+}

src/commonMain/kotlin/cn/rtast/nmdns/util/multicast_socket.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+package cn.rtast.nmdns.util
+
+public expect class MulticastSocket internal constructor() {
+    /**
+     * bind to multicast addr and port
+     */
+    public fun bind(port: Int)
+
+    /**
+     * join multicast group
+     */
+    public fun joinMulticastGroup(group: String)
+
+    /**
+     * leave multicast group
+     */
+    public fun leaveMulticastGroup(group: String)
+
+    /**
+     * send binary packet
+     */
+    public fun send(data: ByteArray, host: String, port: Int)
+
+    /**
+     * receive packet from multicast group
+     */
+    public fun receive(buf: ByteArray): Long
+
+    /**
+     * close socket
+     */
+    public fun close()
+}

src/jvmMain/kotlin/cn/rtast/nmdns/sleep1.jvm.kt

@@ -1,11 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/29/25
- */
-
-package cn.rtast.nmdns
-
-public actual fun sleep1(time: Int) {
-    Thread.sleep(time * 1000L)
-}

src/jvmMain/kotlin/cn/rtast/nmdns/socket.jvm.kt

@@ -1,32 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-
-package cn.rtast.nmdns
-
-import java.net.DatagramPacket
-import java.net.InetAddress
-import java.net.InetSocketAddress
-import java.net.MulticastSocket
-
-public actual class Socket1 internal actual constructor() {
-    private lateinit var socket: MulticastSocket
-    private val group: InetAddress = InetAddress.getByName("224.0.0.251")
-
-    public actual fun bind(ip: String, port: Int): Socket1 {
-        socket = MulticastSocket(InetSocketAddress(ip, port))
-        socket.joinGroup(group)
-        return this
-    }
-
-    public actual fun send(packet: ByteArray) {
-        socket.send(DatagramPacket(packet, packet.size, group, 5353))
-    }
-
-    public actual fun destroy() {
-        socket.close()
-    }
-}

src/jvmMain/kotlin/cn/rtast/nmdns/util/multicast_socket.jvm.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+package cn.rtast.nmdns.util
+
+import java.net.DatagramPacket
+import java.net.InetAddress
+import java.net.InetSocketAddress
+import java.net.NetworkInterface
+import java.net.MulticastSocket as JvmMulticastSocket
+
+public actual class MulticastSocket actual constructor() {
+
+    private var socket: JvmMulticastSocket? = null
+
+    public actual fun bind(port: Int) {
+        socket = JvmMulticastSocket(port)
+        socket?.reuseAddress = true
+    }
+
+    public actual fun joinMulticastGroup(group: String) {
+        val groupAddr = InetAddress.getByName(group)
+        val ni = NetworkInterface.getByName(null)
+        socket?.joinGroup(InetSocketAddress(groupAddr, 0), ni)
+    }
+
+    public actual fun send(data: ByteArray, host: String, port: Int) {
+        val addr = InetAddress.getByName(host)
+        val packet = DatagramPacket(data, data.size, addr, port)
+        socket?.send(packet)
+    }
+
+    public actual fun receive(buf: ByteArray): Long {
+        val packet = DatagramPacket(buf, buf.size)
+        socket?.receive(packet)
+        return packet.length.toLong()
+    }
+
+    public actual fun close() {
+        socket?.close()
+        socket = null
+    }
+
+    public actual fun leaveMulticastGroup(group: String) {
+        val groupAddr = InetAddress.getByName(group)
+        val ni = NetworkInterface.getByName(null)
+        socket?.leaveGroup(InetSocketAddress(groupAddr, 0), ni)
+    }
+}

src/jvmTest/kotlin/test/TestJvm.kt

@@ -7,7 +7,7 @@
 
 package test
 
-import cn.rtast.nmdns.randomMacAddress
+import cn.rtast.nmdns.util.randomMacAddress
 import cn.rtast.nmdns.registerService
 import cn.rtast.nmdns.sleep1
 import org.junit.Test

src/linuxMain/kotlin/cn/rtast/nmdns/socket.linux.kt

@@ -1,68 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-@file:OptIn(ExperimentalForeignApi::class)
-@file:Suppress("unused")
-
-package cn.rtast.nmdns
-
-import kotlinx.cinterop.*
-import platform.linux.inet_addr
-import platform.posix.*
-
-public actual class Socket1 internal actual constructor() {
-    /**
-     * socket fd
-     */
-    private var socket: Int = -1
-
-    public actual fun bind(ip: String, port: Int): Socket1 {
-        socket = socket(AF_INET, SOCK_DGRAM, 0)
-        if (socket < 0) perror("Failed to create udp socket")
-        memScoped {
-            val reuse = alloc<IntVar>()
-            reuse.value = 1
-            if (setsockopt(socket, SOL_SOCKET, SO_REUSEADDR, reuse.ptr, sizeOf<IntVar>().convert()) < 0) {
-                perror("Failed to setsocketopt SO_REUSEADDR")
-            }
-        }
-        memScoped {
-            val addr = alloc<sockaddr_in>()
-            addr.sin_family = AF_INET.convert()
-            addr.sin_port = htons(port.toUShort())
-            addr.sin_addr.s_addr = inet_addr(ip)
-            if (bind(socket, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert()) < 0) {
-                perror("Failed to bind")
-                close(socket)
-            }
-        }
-        memScoped {
-            val mreq = alloc<ip_mreq>()
-            mreq.imr_multiaddr.s_addr = inet_addr("224.0.0.251")
-            mreq.imr_interface.s_addr = htonl(INADDR_ANY)
-            if (setsockopt(socket, IPPROTO_IP, IP_ADD_MEMBERSHIP, mreq.ptr, sizeOf<ip_mreq>().convert()) < 0) {
-                perror("setsockopt IP_ADD_MEMBERSHIP")
-            }
-        }
-
-        return this
-    }
-
-    public actual fun send(packet: ByteArray) {
-        memScoped {
-            val addr = alloc<sockaddr_in>()
-            addr.sin_family = AF_INET.convert()
-            addr.sin_port = htons(5353u)
-            addr.sin_addr.s_addr = inet_addr("224.0.0.251")
-            val cbuf = packet.refTo(0).getPointer(this)
-            sendto(socket, cbuf, packet.size.convert(), 0, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert())
-        }
-    }
-
-    public actual fun destroy() {
-        close(socket)
-    }
-}

src/linuxMain/kotlin/cn/rtast/nmdns/util/multicast_socket.linux.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+@file:OptIn(ExperimentalForeignApi::class)
+
+package cn.rtast.nmdns.util
+
+import kotlinx.cinterop.*
+import platform.linux.inet_addr
+import platform.posix.*
+
+public actual class MulticastSocket actual constructor() {
+    private var fd = -1
+
+    public actual fun bind(port: Int): Unit = memScoped {
+        fd = socket(fd, SOCK_DGRAM, 0)
+        val opt = alloc<IntVar>()
+        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, opt.ptr, sizeOf<IntVar>().convert())
+        val addr = alloc<sockaddr_in>()
+        addr.sin_family = AF_INET.convert()
+        addr.sin_port = htons(port.toUShort())
+        addr.sin_addr.s_addr = INADDR_ANY
+        bind(fd, addr.ptr.reinterpret(), sizeOf<sockaddr_in>().convert())
+    }
+
+    public actual fun joinMulticastGroup(group: String): Unit = memScoped {
+        val merq = alloc<ip_mreq>()
+        merq.imr_multiaddr.s_addr = inet_addr(group)
+        merq.imr_interface.s_addr = INADDR_ANY
+        setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, merq.ptr, sizeOf<ip_mreq>().convert())
+    }
+
+    public actual fun send(data: ByteArray, host: String, port: Int): Unit = memScoped {
+        val addr = alloc<sockaddr_in>()
+        addr.sin_family = AF_INET.convert()
+        addr.sin_port = htons(port.toUShort())
+        addr.sin_addr.s_addr = inet_addr(host)
+        data.usePinned {
+            sendto(
+                fd, it.addressOf(0),
+                data.size.convert(), 0,
+                addr.ptr.reinterpret(),
+                sizeOf<sockaddr_in>().convert()
+            )
+        }
+    }
+
+    public actual fun receive(buf: ByteArray): Long = memScoped {
+        buf.usePinned { recv(fd, it.addressOf(0), buf.size.convert(), 0) }
+    }
+
+    public actual fun close(): Unit = run { if (fd > 0) close(fd) }
+
+    public actual fun leaveMulticastGroup(group: String): Unit = memScoped {
+        val merq = alloc<ip_mreq>()
+        merq.imr_multiaddr.s_addr = inet_addr(group)
+        merq.imr_interface.s_addr = INADDR_ANY
+        setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, merq.ptr, sizeOf<ip_mreq>().convert())
+    }
+}

src/linuxTest/kotlin/test/TestLinux.kt

@@ -10,7 +10,7 @@ package test
 import cn.rtast.nmdns.onBroadcast
 import cn.rtast.nmdns.onRegister
 import cn.rtast.nmdns.onUnregistered
-import cn.rtast.nmdns.randomMacAddress
+import cn.rtast.nmdns.util.randomMacAddress
 import cn.rtast.nmdns.registerService
 import cn.rtast.nmdns.sleep1
 import kotlin.test.Test

src/linuxTest/kotlin/test/TestMacAddr.kt

@@ -7,7 +7,7 @@
 
 package test
 
-import cn.rtast.nmdns.randomMacAddress
+import cn.rtast.nmdns.util.randomMacAddress
 import kotlin.test.Test
 
 class TestMacAddr {

src/linuxTest/kotlin/test/TestNative.kt

@@ -9,7 +9,7 @@ package test
 
 import cn.rtast.nmdns.buildPacket
 import cn.rtast.nmdns.createSocket
-import cn.rtast.nmdns.randomMacAddress
+import cn.rtast.nmdns.util.randomMacAddress
 import cn.rtast.nmdns.sleep1
 import kotlin.test.Test
 

src/mingwMain/kotlin/cn/rtast/nmdns/socket.mingw.kt

@@ -1,87 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-@file:OptIn(ExperimentalForeignApi::class)
-@file:Suppress("unused")
-
-package cn.rtast.nmdns
-
-import kotlinx.cinterop.*
-import platform.posix.*
-import platform.windows.IPPROTO_UDP
-import platform.windows.SOCK_DGRAM
-import platform.windows.WSAStartup
-import platform.windows.inet_addr
-import platform.windows.setsockopt
-
-public actual class Socket1 internal actual constructor() {
-
-    /**
-     * socket fd in windows
-     */
-    private var sock: SOCKET = INVALID_SOCKET
-    private var bound: Boolean = false
-
-    public actual fun bind(ip: String, port: Int): Socket1 = memScoped {
-        val wsaData = nativeHeap.alloc<WSADATA>()
-        if (WSAStartup(0x202u, wsaData.ptr) != 0) {
-            perror("Failed to create socket")
-        }
-        sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
-        if (sock == INVALID_SOCKET) {
-            perror("Failed to create socket")
-            WSACleanup()
-        }
-
-        val result = setsockopt(
-            sock,
-            SOL_SOCKET,
-            SO_REUSEADDR,
-            "1",
-            sizeOf<IntVar>().convert()
-        )
-        if (result != 0) println("setsockopt failed")
-
-        val addr = alloc<SOCKADDR_IN>()
-        addr.sin_family = AF_INET.convert()
-        addr.sin_port = htons(port.toUShort())
-        addr.sin_addr.S_un.S_addr = inet_addr(ip)
-
-        if (bind(sock, addr.ptr.reinterpret(), sizeOf<SOCKADDR_IN>().convert()) == SOCKET_ERROR) {
-            println("Bind failed")
-            closesocket(sock)
-            WSACleanup()
-        }
-
-        bound = true
-        this@Socket1
-    }
-
-    public actual fun send(packet: ByteArray): Unit = memScoped {
-        if (!bound) throw IllegalStateException("Socket not bound")
-        val dest = alloc<SOCKADDR_IN>()
-        dest.sin_family = AF_INET.convert()
-        dest.sin_port = htons(5353u)
-        dest.sin_addr.S_un.S_addr = inet_addr("224.0.0.251")
-        packet.usePinned { pinned ->
-            val sent = sendto(
-                sock, pinned.addressOf(0),
-                packet.size.convert(),
-                0, dest.ptr.reinterpret(),
-                sizeOf<SOCKADDR_IN>().convert()
-            )
-            if (sent == SOCKET_ERROR) perror("Send failed")
-        }
-    }
-
-    public actual fun destroy() {
-        if (sock != INVALID_SOCKET) {
-            closesocket(sock)
-            sock = INVALID_SOCKET
-        }
-        WSACleanup()
-    }
-}

src/mingwMain/kotlin/cn/rtast/nmdns/util/multicast_socket.mingw.kt

@@ -0,0 +1,68 @@
+/*
+ * Copyright © 2026 RTAkland
+ * Author: RTAkland
+ * Date: 2026/3/13
+ */
+
+
+@file:OptIn(ExperimentalForeignApi::class)
+
+package cn.rtast.nmdns.util
+
+import kotlinx.cinterop.*
+import platform.posix.*
+import platform.windows.AF_INET
+import platform.windows.IPPROTO_UDP
+import platform.windows.SOCK_DGRAM
+import platform.windows.WSAStartup
+import platform.windows.setsockopt
+
+public actual class MulticastSocket actual constructor() {
+
+    private var fd: SOCKET = INVALID_SOCKET
+
+    public actual fun bind(port: Int): Unit = memScoped {
+        val wsaData = alloc<WSADATA>()
+        if (WSAStartup(0x202u, wsaData.ptr) != 0) perror("Failed to create socket")
+        fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
+        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, "1", sizeOf<IntVar>().convert())
+        val addr = alloc<SOCKADDR_IN>()
+        addr.sin_family = AF_INET.convert()
+        addr.sin_port = htons(port.toUShort())
+        addr.sin_addr.S_un.S_addr = INADDR_ANY
+        bind(fd, addr.ptr.reinterpret(), sizeOf<SOCKADDR_IN>().convert())
+    }
+
+    public actual fun joinMulticastGroup(group: String): Unit = memScoped {
+        // ref: clibs/win32_join_multicast.c:7
+        win32_join_multicast_group.join_multicast_group(fd, group)
+    }
+
+    public actual fun send(data: ByteArray, host: String, port: Int): Unit = memScoped {
+        val addr = alloc<SOCKADDR_IN>()
+        addr.sin_family = AF_INET.convert()
+        addr.sin_port = htons(port.toUShort())
+        addr.sin_addr.S_un.S_addr = inet_addr(host)
+        data.usePinned {
+            // ref: clibs/win32_join_multicast.c:18
+            win32_join_multicast_group.socket_sendto(
+                fd, it.addressOf(0).reinterpret(),
+                data.size, host, port.toUShort()
+            )
+        }
+    }
+
+    public actual fun receive(buf: ByteArray): Long = memScoped {
+        buf.usePinned { recv(fd, it.addressOf(0), buf.size.convert(), 0) }.toLong()
+    }
+
+    public actual fun close() {
+        closesocket(fd)
+        WSACleanup()
+    }
+
+    public actual fun leaveMulticastGroup(group: String) {
+        // ref: clibs/win32_join_multicast.c:31
+        win32_join_multicast_group.leave_multicast_group(fd, group)
+    }
+}

src/mingwTest/kotlin/test/TestWindows.kt

@@ -7,7 +7,7 @@
 
 package test
 
-import cn.rtast.nmdns.randomMacAddress
+import cn.rtast.nmdns.util.randomMacAddress
 import cn.rtast.nmdns.registerService
 import cn.rtast.nmdns.sleep1
 import kotlin.test.Test

src/nativeMain/kotlin/cn/rtast/nmdns/list.kt

@@ -1,28 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/30/25
- */
-
-
-@file:OptIn(ExperimentalNativeApi::class)
-
-package cn.rtast.nmdns
-
-import kotlin.experimental.ExperimentalNativeApi
-
-/**
- * create an empty list in c
- */
-@CExport
-@CName("create_txt_records")
-public fun createTXTRecords(): List<String> = listOf()
-
-/**
- * add txt record to list
- */
-@CExport
-@CName("add_txt_record")
-public fun addTxtRecord(list: List<String>, value: String) {
-    list.toMutableList().add(value)
-}

src/nativeMain/kotlin/cn/rtast/nmdns/sleep1.native.kt

@@ -1,16 +0,0 @@
-/*
- * Copyright © 2025 RTAkland
- * Author: RTAkland
- * Date: 9/29/25
- */
-
-package cn.rtast.nmdns
-
-import platform.posix.sleep
-import kotlin.experimental.ExperimentalNativeApi
-
-@OptIn(ExperimentalNativeApi::class)
-@CName("sleep1")
-public actual fun sleep1(time: Int) {
-    sleep(time.toUInt())
-}