Linux: Fix: connectHandler after adv.Start (#369)

* Linux: Fix: connectHandler after adv.Start

In Linux the Adapter.connectHandler is never called after Advertisement.Start.

This fix preserves the existing interfaces and adds D-Bus signals to handle
connect/disconnect events once the Peripheral is advertising.

- Fix Linux Advertise.Start to call the connectHandler, if set
- Update inline documentation for Adapter.SetConnectHandler
- Update README usage example

Signed-off-by: Nick Ross <[email protected]>

* Revert README examples to use println

Signed-off-by: Nick Ross <[email protected]>

* Add resource cleanup in example

* Advertising, signal handling, and README corrections

- Add alias update on adveristing
- Extend property handling for signals
- Correct README example

Signed-off-by: Nick Ross <[email protected]>

* Add connectHandler to advertisement example

Signed-off-by: Nick Ross <[email protected]>

* Invoke handler on device initial connection

Signed-off-by: Nick Ross <[email protected]>

---------

Signed-off-by: Nick Ross <[email protected]>

Author: nckrss

README.md

@@ -56,6 +56,7 @@ This example shows a peripheral that advertises itself as being available for co
 package main
 
 import (
+	"context"
 	"time"
 
 	"tinygo.org/x/bluetooth"
@@ -67,6 +68,17 @@ func main() {
   	// Enable BLE interface.
 	must("enable BLE stack", adapter.Enable())
 
+	ctx, cancel := context.WithCancel(context.Background())
+	adapter.SetConnectHandler(func(device bluetooth.Device, connected bool) {
+		if connected {
+			println("device connected:", device.Address.String())
+			return
+		}
+
+		println("device disconnected:", device.Address.String())
+		cancel()
+	})
+
   	// Define the peripheral device info.
 	adv := adapter.DefaultAdvertisement()
 	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
@@ -75,12 +87,12 @@ func main() {
 
   	// Start advertising
 	must("start adv", adv.Start())
+	
+	// Stop advertising to release resources
+	defer adv.Stop()
 
 	println("advertising...")
-	for {
-		// Sleep forever.
-		time.Sleep(time.Hour)
-	}
+	<- ctx.Done()
 }
 
 func must(action string, err error) {

adapter.go

@@ -1,8 +1,8 @@
 package bluetooth
 
 // SetConnectHandler sets a handler function to be called whenever the adaptor connects
-// or disconnects. You must call this before you call adaptor.Connect() for centrals
-// or adaptor.Start() for peripherals in order for it to work.
+// or disconnects. You must call this before you call adapter.Connect() for centrals
+// or advertisement.Start() for peripherals in order for it to work.
 func (a *Adapter) SetConnectHandler(c func(device Device, connected bool)) {
 	a.connectHandler = c
 }

examples/advertisement/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"time"
 
 	"tinygo.org/x/bluetooth"
@@ -10,6 +11,18 @@ var adapter = bluetooth.DefaultAdapter
 
 func main() {
 	must("enable BLE stack", adapter.Enable())
+
+	ctx, cancel := context.WithCancel(context.Background())
+	adapter.SetConnectHandler(func(device bluetooth.Device, connected bool) {
+		if connected {
+			println("device connected:", device.Address.String())
+			return
+		}
+
+		println("device disconnected:", device.Address.String())
+		cancel()
+	})
+
 	adv := adapter.DefaultAdvertisement()
 	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
 		LocalName: "Go Bluetooth",
@@ -18,12 +31,17 @@ func main() {
 		},
 	}))
 	must("start adv", adv.Start())
+	defer adv.Stop()
 
 	println("advertising...")
 	address, _ := adapter.Address()
 	for {
-		println("Go Bluetooth /", address.MAC.String())
-		time.Sleep(time.Second)
+		select {
+		case <-time.After(1 * time.Second):
+			println("Go Bluetooth /", address.MAC.String())
+		case <-ctx.Done():
+			return
+		}
 	}
 }
 

gap_linux.go

@@ -12,6 +12,39 @@ import (
 	"github.com/godbus/dbus/v5/prop"
 )
 
+const (
+	// Match rule constants for D-Bus signals.
+	//
+	// See [DBusPropertiesLink] for more information.
+
+	dbusPropertiesChangedInterfaceName = 0
+	dbusPropertiesChangedDictionary    = 1
+	dbusPropertiesChangedInvalidated   = 2
+
+	dbusInterfacesAddedDictionary = 1
+
+	dbusSignalInterfacesAdded   = "org.freedesktop.DBus.ObjectManager.InterfacesAdded"
+	dbusSignalPropertiesChanged = "org.freedesktop.DBus.Properties.PropertiesChanged"
+
+	bluezDevice1Interface = "org.bluez.Device1"
+	bluezDevice1Address   = "Address"
+	bluezDevice1Connected = "Connected"
+)
+
+var (
+	// See [DBusPropertiesLink] for more information.
+	matchOptionsPropertiesChanged = []dbus.MatchOption{dbus.WithMatchInterface("org.freedesktop.DBus.Properties"),
+		dbus.WithMatchMember("PropertiesChanged"),
+		dbus.WithMatchArg(dbusPropertiesChangedInterfaceName, "org.bluez.Device1")}
+
+	// See [DBusObjectManagerLink] for more information.
+	matchOptionsInterfacesAdded = []dbus.MatchOption{dbus.WithMatchInterface("org.freedesktop.DBus.ObjectManager"),
+		dbus.WithMatchMember("InterfacesAdded")}
+)
+
+// [DBusPropertiesLink]: https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties
+// [DBusObjectManagerLink]: https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-objectmanager
+
 var errAdvertisementNotStarted = errors.New("bluetooth: advertisement is not started")
 var errAdvertisementAlreadyStarted = errors.New("bluetooth: advertisement is already started")
 var errAdaptorNotPowered = errors.New("bluetooth: adaptor is not powered")
@@ -30,6 +63,9 @@ type Advertisement struct {
 	properties *prop.Properties
 	path       dbus.ObjectPath
 	started    bool
+
+	// D-Bus Signals
+	sigCh chan *dbus.Signal
 }
 
 // DefaultAdvertisement returns the default advertisement instance but does not
@@ -93,6 +129,17 @@ func (a *Advertisement) Configure(options AdvertisementOptions) error {
 	}
 	a.properties = props
 
+	if options.LocalName != "" {
+		// In BlueZ AdvertisementOptions.LocalName will be sent in Extended
+		// Advertising Data and it will not change the Adapter alias.  Setting
+		// this property will update the name in the initial advertising data.
+		call := a.adapter.adapter.Call("org.freedesktop.DBus.Properties.Set", 0,
+			"org.bluez.Adapter1", "Alias", dbus.MakeVariant(options.LocalName))
+		if call.Err != nil {
+			return fmt.Errorf("set adapter alias: %w", call.Err)
+		}
+	}
+
 	return nil
 }
 
@@ -107,6 +154,21 @@ func (a *Advertisement) Start() error {
 		return fmt.Errorf("bluetooth: could not start advertisement: %w", err)
 	}
 
+	if a.adapter.connectHandler != nil {
+		a.sigCh = make(chan *dbus.Signal)
+		a.adapter.bus.Signal(a.sigCh)
+
+		if err := a.adapter.bus.AddMatchSignal(matchOptionsPropertiesChanged...); err != nil {
+			return fmt.Errorf("bluetooth: add dbus match signal: PropertiesChanged: %w", err)
+		}
+
+		if err := a.adapter.bus.AddMatchSignal(matchOptionsInterfacesAdded...); err != nil {
+			return fmt.Errorf("bluetooth: add dbus match signal: InterfacesAdded: %w", err)
+		}
+
+		go a.handleDBusSignals()
+	}
+
 	// Make us discoverable.
 	err = a.adapter.adapter.SetProperty("org.bluez.Adapter1.Discoverable", dbus.MakeVariant(true))
 	if err != nil {
@@ -126,6 +188,17 @@ func (a *Advertisement) Stop() error {
 		return fmt.Errorf("bluetooth: could not stop advertisement: %w", err)
 	}
 	a.started = false
+
+	if a.sigCh != nil {
+		defer close(a.sigCh)
+		if err := a.adapter.bus.RemoveMatchSignal(matchOptionsPropertiesChanged...); err != nil {
+			return fmt.Errorf("bluetooth: remove dbus match signal: PropertiesChanged: %w", err)
+		}
+		if err := a.adapter.bus.RemoveMatchSignal(matchOptionsInterfacesAdded...); err != nil {
+			return fmt.Errorf("bluetooth: remove dbus match signal: InterfacesAdded: %w", err)
+		}
+		a.adapter.bus.RemoveSignal(a.sigCh)
+	}
 	return nil
 }
 
@@ -357,7 +430,7 @@ func makeScanResult(props map[string]dbus.Variant) ScanResult {
 	}
 }
 
-// Device is a connection to a remote peripheral.
+// Device is a connection to a remote bluetooth device.
 type Device struct {
 	Address Address // the MAC address of the device
 
@@ -496,3 +569,90 @@ func (a *Adapter) SetRandomAddress(mac MAC) error {
 
 	return nil
 }
+
+func (a *Advertisement) handleDBusSignals() {
+	for {
+		select {
+		case sig, ok := <-a.sigCh:
+			if !ok {
+				return // channel closed
+			}
+
+			device := Device{
+				device:  a.adapter.bus.Object("org.bluez", sig.Path),
+				adapter: a.adapter,
+			}
+
+			switch sig.Name {
+			case dbusSignalInterfacesAdded:
+				interfaces := sig.Body[dbusInterfacesAddedDictionary].(map[string]map[string]dbus.Variant)
+
+				// InterfacesAdded signal also contains all known properties so
+				// so we do not need to call org.freedesktop.DBus.Properties.GetAll
+				props, ok := interfaces[bluezDevice1Interface]
+				if !ok {
+					continue
+				}
+
+				if err := device.parseProperties(&props); err != nil {
+					continue
+				}
+
+				if connected, ok := props[bluezDevice1Connected].Value().(bool); ok {
+					a.adapter.connectHandler(device, connected)
+				}
+			case dbusSignalPropertiesChanged:
+				// Skip any signals that are not the Device1 interface.
+				if interfaceName, ok := sig.Body[dbusPropertiesChangedInterfaceName].(string); !ok || interfaceName != bluezDevice1Interface {
+					continue
+				}
+
+				// Get all changed properties and skip any signals that are not
+				// compliant with the Device1 interface.
+				changes, ok := sig.Body[dbusPropertiesChangedDictionary].(map[string]dbus.Variant)
+				if !ok {
+					continue
+				}
+
+				// Call the connect handler if the Connected property has changed.
+				if connected, ok := changes[bluezDevice1Connected].Value().(bool); ok {
+					// The only property received is the changed property "Connected",
+					// so we have to get the other properties from D-Bus.
+					var props map[string]dbus.Variant
+					if err := device.device.Call("org.freedesktop.DBus.Properties.GetAll",
+						0,
+						bluezDevice1Interface).Store(&props); err != nil {
+						continue
+					}
+
+					if err := device.parseProperties(&props); err != nil {
+						continue
+					}
+
+					a.adapter.connectHandler(device, connected)
+				}
+			}
+		}
+	}
+}
+
+// parseProperties will set fields from provided properties
+//
+// For all possible properties see:
+// https://github.com/luetzel/bluez/blob/master/doc/device-api.txt
+func (d *Device) parseProperties(props *map[string]dbus.Variant) error {
+	for prop, v := range *props {
+		switch prop {
+		case bluezDevice1Address:
+			if addrStr, ok := v.Value().(string); ok {
+				mac, err := ParseMAC(addrStr)
+				if err != nil {
+					return fmt.Errorf("ParseMAC: %w", err)
+				}
+				d.Address = Address{MACAddress: MACAddress{MAC: mac}}
+			}
+		}
+	}
+
+	return nil
+}