How to Identify Connected Android Hotspot Devices Using Kotlin & NSD

How Did We Encounter The Device Identification Challenge In Our Logistics Platform

During a recent project for a global logistics and supply chain enterprise, we were tasked with building an offline-first mobile synchronization platform. The operational model required lead technicians in remote field locations to act as local data hubs. Using a ruggedized Android tablet, the lead technician would enable a mobile hotspot. Subordinate technicians would then connect their mobile devices to this host tablet to synchronize daily inventory and delivery logs locally, bypassing the need for a cellular connection.

While the initial peer-to-peer connection worked flawlessly, we realized a significant usability flaw during field testing. The host app, built in Kotlin, successfully scanned and displayed the client devices connected to the hotspot. However, it only displayed raw IP and MAC addresses. Field supervisors had a hard time resolving the actual readable WiFi names or device names of the connected client devices. Instead of seeing “Technician A Galaxy S23”, they saw “192.168.43.15”.

This ambiguity made it impossible for the lead technician to verify exactly who had synchronized their data before dispatching the team. Resolving client device names on a mobile hotspot using Android is a notorious challenge due to evolving OS privacy restrictions. This challenge inspired this article, detailing how we bypassed legacy network limitations to build a reliable device identification module, a strategy that companies expect when they hire software developer teams for enterprise-grade mobile solutions.

Why Is Resolving Connected Client Names Critical For Local Network Operations

In consumer applications, simply knowing a device is connected to a hotspot might be sufficient. In an enterprise logistics system, identity is tied to accountability. The architecture of our application relied on the host device acting as a local edge server. The host needed to display a real-time dashboard of connected personnel to orchestrate data synchronization streams effectively.

When an Android device operates as a mobile hotspot, it runs a lightweight DHCP server (often dnsmasq) to assign IP addresses to connecting clients. Historically, identifying these clients involved reading network configuration files or performing simple reverse DNS lookups. However, in an enterprise setting, relying on IP addresses is insufficient because IPs are assigned dynamically and offer no contextual information about the user or the specific hardware device.

What Were The Symptoms And Architectural Bottlenecks We Discovered

When the issue surfaced, our initial approach was to rely on standard Android and Java networking libraries. We captured the IP addresses of connected clients using standard network scanning techniques and attempted to resolve the hostnames. The symptoms of failure were immediately apparent in our production logs.

First, calling the standard Java network resolution functions consistently returned the raw IP address instead of a human-readable hostname. The logs indicated connection timeouts during DNS resolution. Because the Android hotspot does not act as a full-featured local DNS server that registers client hostnames upon DHCP negotiation, reverse DNS queries essentially fell into a void.

Second, we noticed that modern Android versions actively obfuscate network hardware details to protect user privacy. Starting from Android 10, access to the ARP cache and hardware identifiers like MAC addresses became heavily restricted. Randomization of MAC addresses meant we could not even map a hardware address to a known device database. These architectural bottlenecks meant that any solution relying on OS-level network tables was destined to fail across fragmented Android OS versions.

How Did We Evaluate Potential Solutions For Android Network Discovery

To deliver a resilient solution, we evaluated several network discovery approaches. When decision-makers look to hire kotlin developers for android apps, they expect teams to look beyond surface-level APIs and engineer robust application-layer solutions.

Can Reverse DNS Lookups Solve The Naming Issue

We first considered utilizing the standard InetAddress class to perform a canonical hostname lookup. The approach involved scanning the local subnet, pinging active IPs, and requesting their hostnames. We quickly discarded this. Android hotspot routing does not consistently register client hostnames, meaning the lookup either fails or simply echoes the IP address back to the application.

Is Parsing The ARP Table Still Viable In Modern Android

Historically, developers could read the /proc/net/arp file to map IP addresses to MAC addresses and cross-reference device vendors. We evaluated whether we could read the dnsmasq lease file located in system directories. This solution was abandoned because modern Android security models require root access to read these specific networking files, which was not viable for our client’s standard enterprise devices.

Can Network Service Discovery Provide Reliable Metadata

We realized we needed to move the identification logic from the OS network layer to the application layer. We considered using Android Network Service Discovery, also known as mDNS or Bonjour. Since our enterprise controls both the host application and the client application, we could program the client app to broadcast its human-readable name over the local hotspot network, and have the host app listen for these broadcasts. This proved to be the most viable, scalable, and secure approach.

How Did We Implement A Robust Network Service Discovery In Kotlin

We implemented a two-part solution utilizing Android NsdManager. The client device, upon connecting to the hotspot, registers a local network service containing its configurable technician name. The host device, operating the hotspot, continuously discovers these services to build a rich, human-readable dashboard.

Below is the sanitized, generic implementation of our discovery logic.

// Client-Side Registration Implementation
class DeviceNameBroadcaster(private val context: Context) {
    private var nsdManager: NsdManager? = null
    private var registrationListener: NsdManager.RegistrationListener? = null
    fun broadcastDeviceName(technicianName: String) {
        nsdManager = context.getSystemService(Context.NSD_SERVICE) as NsdManager
        
        val serviceInfo = NsdServiceInfo().apply {
            serviceName = "Logistics_Tech_$technicianName"
            serviceType = "_http._tcp."
            port = 8080 // Arbitrary port for application layer handshake
        }
        registrationListener = object : NsdManager.RegistrationListener {
            override fun onServiceRegistered(NsdServiceInfo: NsdServiceInfo) {
                // Service successfully broadcasted
            }
            override fun onRegistrationFailed(serviceInfo: NsdServiceInfo, errorCode: Int) {
                // Handle broadcast failure
            }
            override fun onServiceUnregistered(arg0: NsdServiceInfo) {}
            override fun onUnregistrationFailed(serviceInfo: NsdServiceInfo, errorCode: Int) {}
        }
        nsdManager?.registerService(serviceInfo, NsdManager.PROTOCOL_DNS_SD, registrationListener)
    }
}

On the host device, we implemented a discovery listener that captures these human-readable names and maps them to the underlying IP addresses connecting to the hotspot.

// Host-Side Discovery Implementation
class ClientDeviceDiscoverer(private val context: Context) {
    private val nsdManager = context.getSystemService(Context.NSD_SERVICE) as NsdManager
    private val connectedClients = mutableListOf<String>()
    fun startDiscovery() {
        val discoveryListener = object : NsdManager.DiscoveryListener {
            override fun onDiscoveryStarted(regType: String) {}
            override fun onServiceFound(service: NsdServiceInfo) {
                if (service.serviceType == "_http._tcp." && service.serviceName.startsWith("Logistics_Tech_")) {
                    nsdManager.resolveService(service, object : NsdManager.ResolveListener {
                        override fun onResolveFailed(serviceInfo: NsdServiceInfo, errorCode: Int) {}
                        override fun onServiceResolved(serviceInfo: NsdServiceInfo) {
                            val deviceName = serviceInfo.serviceName.replace("Logistics_Tech_", "")
                            val deviceIp = serviceInfo.host.hostAddress
                            
                            // Map readable name to IP for UI display
                            connectedClients.add("Name: $deviceName, IP: $deviceIp")
                        }
                    })
                }
            }
            override fun onServiceLost(service: NsdServiceInfo) {}
            override fun onDiscoveryStopped(serviceType: String) {}
            override fun onStartDiscoveryFailed(serviceType: String, errorCode: Int) {}
            override fun onStopDiscoveryFailed(serviceType: String, errorCode: Int) {}
        }
        nsdManager.discoverServices("_http._tcp.", NsdManager.PROTOCOL_DNS_SD, discoveryListener)
    }
}

Validation steps involved testing this across multiple Android OS versions ranging from Android 9 to Android 14. By shifting from OS-level constraints to an application-layer broadcast, we bypassed ARP cache limitations and MAC randomization entirely. Performance impact was negligible, as mDNS utilizes lightweight UDP packets, ensuring battery drain remained strictly within enterprise operational limits.

What Are The Key Takeaways For Mobile Development Teams

Navigating network constraints requires a shift in architectural thinking. When organizations hire android developers for mobile connectivity projects, they should ensure the team understands these core principles:

• Stop Fighting The OS Privacy changes in Android regarding network hardware identifiers are permanent. Relying on legacy workarounds like reading ARP caches introduces high technical debt.
• Leverage Application Layer Protocols When system layers abstract data away, build application-layer handshakes. Using NsdManager or custom UDP beacons provides far more control over device identification.
• Design For Offline First Do not assume a centralized server will always be available to resolve device metadata. Edge networks must be self-sufficient in resolving their own topologies.
• Manage State Delays Gracefully mDNS discovery can take a few seconds. Ensure your UI gracefully handles loading states while resolving hostnames, rather than failing abruptly.
• Adopt Cross-Version Validation Mobile hotspot behaviors vary drastically between device manufacturers. Custom OEM skins often modify DHCP lease behaviors, making custom broadcasts the only uniform solution.

How Can Your Team Overcome Similar Mobile Networking Hurdles

Identifying connected devices on an Android hotspot transitioned from a simple OS query to a complex architectural challenge due to modern privacy features. By abandoning legacy network parsing in favor of Network Service Discovery, we delivered a highly resilient offline synchronization system for our logistics client. This problem-solving approach is critical when you hire app developer to create a mobile app that operates in complex, real-world edge environments. If your organization is facing similar architectural bottlenecks or looking to scale your engineering capabilities, contact us to explore how our dedicated development teams can drive your next deployment.

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