Android使用Wi-Fi配对的原理和实现

原理

Android Studio中插件实现的原理

源码

https://cs.android.com/android-studio/platform/tools/adt/idea/+/mirror-goog-studio-master-dev:android-adb/src/com/android/tools/idea/adb/wireless/WiFiPairingServiceImpl.kt

重点函数说明

2.1 检查adb mdns的支持状况

override fun checkMdnsSupport(): ListenableFuture<MdnsSupportState> {
    // TODO: Investigate updating (then using) ddmlib instead of spawning an adb client command, so that
    //       we don't have to rely on parsing command line output
    LOG.info("Checking if mDNS is supported (`adb mdns check` command)")
    val futureResult = adbService.executeCommand(listOf("mdns", "check"))
    return futureResult.transform(taskExecutor) { result ->
    when {
        result.errorCode != 0 -> {
        LOG.warn("`adb mdns check` returned a non-zero error code (${result.errorCode})")
        val isUnknownCommand = result.stderr.any { line -> line.contains(Regex("unknown.*command")) }
        if (isUnknownCommand)
            MdnsSupportState.AdbVersionTooLow
        else
            MdnsSupportState.AdbInvocationError
        }
        result.stdout.isEmpty() -> {
        LOG.warn("`adb mdns check` returned an empty output (why?)")
        MdnsSupportState.AdbInvocationError
        }
        // See https://android-review.googlesource.com/c/platform/system/core/+/1274009/5/adb/client/transport_mdns.cpp#553
        result.stdout.any { it.contains("mdns daemon version") } -> {
        MdnsSupportState.Supported
        }
        else -> {
        MdnsSupportState.NotSupported
        }
    }
    }.catching(taskExecutor, Throwable::class.java) { t ->
    LOG.warn("Error executing `adb mdns check`", t)
    MdnsSupportState.AdbInvocationError
    }.transform(taskExecutor) { supportState ->
    // This `tansform` is just for logging purposes
    LOG.info("Checking if mDNS is supportState result: ${supportState}")
    supportState
    }
}

2.2 adb mdns services列出支持mdns的设备

override fun scanMdnsServices(): ListenableFuture<List<MdnsService>> {
    // TODO: Investigate updating (then using) ddmlib instead of spawning an adb client command, so that
    //       we don't have to rely on parsing command line output
    val futureResult = adbService.executeCommand(listOf("mdns", "services"))
    return futureResult.transform(taskExecutor) { result ->
    // Output example:
    //  List of discovered mdns services
    //  adb-939AX05XBZ-vWgJpq	_adb-tls-connect._tcp.	192.168.1.86:39149
    //  adb-939AX05XBZ-vWgJpq	_adb-tls-pairing._tcp.	192.168.1.86:37313
    // Regular expression
    //  adb-<everything-until-space><spaces>__adb-tls-pairing._tcp.<spaces><everything-until-colon>:<port>
    val lineRegex = Regex("([^\\t]+)\\t*_adb-tls-pairing._tcp.\\t*([^:]+):([0-9]+)")

    if (result.errorCode != 0) {
        throw AdbCommandException("Error discovering services", result.errorCode, result.stderr)
    }

    if (result.stdout.isEmpty()) {
        throw AdbCommandException("Empty output from \"adb mdns services\" command", -1, result.stderr)
    }

    return@transform result.stdout
        .drop(1)
        .mapNotNull { line ->
        val matchResult = lineRegex.find(line)
        matchResult?.let {
            try {
            val serviceName = it.groupValues[1]
            val ipAddress = InetAddress.getByName(it.groupValues[2])
            val port = it.groupValues[3].toInt()
            val serviceType = if (serviceName.startsWith(studioServiceNamePrefix)) ServiceType.QrCode else ServiceType.PairingCode
            MdnsService(serviceName, serviceType, ipAddress, port)
            }
            catch (ignored: Exception) {
            LOG.warn("mDNS service entry ignored due do invalid characters: ${line}")
            null
            }
        }
        }
    }
}

2.3 adb pair ipAddr:port password，用来配对PC和Android手机

    override fun pairMdnsService(mdnsService: MdnsService, password: String): ListenableFuture<PairingResult> {
    LOG.info("Start mDNS pairing: ${mdnsService}")

    val deviceAddress = "${mdnsService.ipAddress.hostAddress}:${mdnsService.port}"
    // TODO: Update this when password can be passed as an argument
    val passwordInput = password + LineSeparator.getSystemLineSeparator().separatorString
    // TODO: Investigate updating (then using) ddmlib instead of spawning an adb client command, so that
    //       we don't have to rely on parsing command line output
    val futureResult = adbService.executeCommand(listOf("pair", deviceAddress), passwordInput)

    return futureResult.transform(taskExecutor) { result ->
    LOG.info("mDNS pairing exited with code ${result.errorCode}")
    result.stdout.take(5).forEachIndexed { index, line ->
        LOG.info("  stdout line #$index: $line") }

    if (result.errorCode != 0) {
        throw AdbCommandException("Error pairing device", result.errorCode, result.stderr)
    }

    if (result.stdout.isEmpty()) {
        throw AdbCommandException("Empty output from \"adb pair\" command", -1, result.stderr)
    }

    // Output example:
    //  Enter pairing code: Successfully paired to 192.168.1.86:41915 [guid=adb-939AX05XBZ-vWgJpq]
    // Regular expression
    //  <Prefix><everything-until-colon>:<port>[guid=<everything-until-close-bracket>]
    val lineRegex = Regex("Successfully paired to ([^:]*):([0-9]*) \\[guid=([^\\]]*)\\]")
    val matchResult = lineRegex.find(result.stdout[0])
    matchResult?.let {
        try {
        val ipAddress = InetAddress.getByName(it.groupValues[1])
        val port = it.groupValues[2].toInt()
        val serviceGuid = it.groupValues[3]
        PairingResult(ipAddress, port, serviceGuid)
        }
        catch (e: Exception) {
        throw InvalidDataException("Pairing result is invalid", e)
        }
    } ?: throw InvalidDataException("Pairing result is invalid")
    }
}

2.4 生成二维码的内容格式

/**
* Format is "WIFI:T:ADB;S:service;P:password;;" (without the quotes)
*/
private fun createPairingString(service: String, password:      String): String {
    return "WIFI:T:ADB;S:${service};P:${password};;"
}