USB networking (NCM)

static final NetworkRequest NCM_REQUEST =
    new NetworkRequest.Builder()
        .removeCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
        .removeCapability(NetworkCapabilities.NET_CAPABILITY_TRUSTED)
        .addTransportType(NetworkCapabilities.TRANSPORT_USB)
        .build();

ConnectivityManager cm = context.getSystemService(ConnectivityManager.class);

void requestNetwork() {
    cm.requestNetwork(NCM_REQUEST, mCallback, new Handler(Looper.getMainLooper()));
}

private final ConnectivityManager.NetworkCallback mCallback =
    new ConnectivityManager.NetworkCallback() {
        @Override
        public void onAvailable(Network network) {
            // The USB-NCM network is up and ready to use.
        }

        @Override
        public void onCapabilitiesChanged(Network network, NetworkCapabilities caps) {
            // Reports link bandwidth — used to detect USB 2 vs USB 3.
        }

        @Override
        public void onLinkPropertiesChanged(Network network, LinkProperties lp) {
            // lp.getInterfaceName() is the NCM interface; lp.getLinkAddresses()
            // contains the IPv6 link-local address to bind/connect with.
        }

        @Override
        public void onLost(Network network) {
            // The network went away (cable unplugged, USB mode changed, etc.).
        }

        @Override
        public void onUnavailable() {
            // The request could not be satisfied — most commonly the user
            // denied the consent dialog.
        }
    };

@Override
public void onUnavailable() {
    // The system reports onUnavailable when the request can't be satisfied,
    // most commonly when the user denies the USB-NCM consent dialog. At this
    // point the network request is already released. Update the UI to reflect that.
    if (mRequested) {
        mRequested = false;
    }
    mStatusText.setText(R.string.network_status_unavailable);
}

@Override
public void onCapabilitiesChanged(Network network, NetworkCapabilities caps) {
    int downKbps = caps.getLinkDownstreamBandwidthKbps();
    int upKbps   = caps.getLinkUpstreamBandwidthKbps();
    // downKbps / upKbps reflect the negotiated USB cable/port speed.
}

private static final int USB3_MIN_KBPS = 1_000_000; // 1 Gbps threshold

@Override
public void onCapabilitiesChanged(Network network, NetworkCapabilities caps) {
    int downKbps = caps.getLinkDownstreamBandwidthKbps();
    if (downKbps > 0 && downKbps < USB3_MIN_KBPS) {
        // ~480 Mbps => USB 2 cable/port. Prompt the user to switch to a
        // USB 3 cable for high-bandwidth transfers.
        showUseUsb3CableHint(downKbps);
    }
}

void releaseNetwork() {
    cm.unregisterNetworkCallback(mCallback);
}