feat: support specifying Zeroconf port

Closes #154

README.md

@@ -62,6 +62,7 @@ An example configuration (not required) looks like this:
 
 ```yaml
 zeroconf_enabled: false # Whether to keep the device discoverable at all times, even if authenticated via other means
+zeroconf_port: 0 # The port to use for Zeroconf, 0 for random
 credentials:
   type: zeroconf
   zeroconf:

cmd/daemon/main.go

@@ -214,7 +214,7 @@ func (app *App) withAppPlayer(ctx context.Context, appPlayerFunc func(context.Co
 	}
 
 	// start zeroconf server and dispatch
-	z, err := zeroconf.NewZeroconf(app.cfg.DeviceName, app.deviceId, app.deviceType)
+	z, err := zeroconf.NewZeroconf(app.cfg.ZeroconfPort, app.cfg.DeviceName, app.deviceId, app.deviceType)
 	if err != nil {
 		return fmt.Errorf("failed initializing zeroconf: %w", err)
 	}
@@ -359,6 +359,7 @@ type Config struct {
 	NormalisationPregain  float32   `koanf:"normalisation_pregain"`
 	ExternalVolume        bool      `koanf:"external_volume"`
 	ZeroconfEnabled       bool      `koanf:"zeroconf_enabled"`
+	ZeroconfPort          int       `koanf:"zeroconf_port"`
 	DisableAutoplay       bool      `koanf:"disable_autoplay"`
 	Server                struct {
 		Enabled     bool   `koanf:"enabled"`

config_schema.json

@@ -134,6 +134,11 @@
           "description": "Whether Zeroconf discovery should always be enabled (even when logging in with credentials)",
           "default": false
         },
+        "zeroconf_port": {
+          "type": "integer",
+          "description": "The port to use for the Zeroconf service (empty for random)",
+          "default": 0
+        },
         "credentials": {
           "type": "object",
           "properties": {

zeroconf/zeroconf.go

@@ -45,7 +45,7 @@ type NewUserRequest struct {
 	result chan bool
 }
 
-func NewZeroconf(deviceName, deviceId string, deviceType devicespb.DeviceType) (_ *Zeroconf, err error) {
+func NewZeroconf(port int, deviceName, deviceId string, deviceType devicespb.DeviceType) (_ *Zeroconf, err error) {
 	z := &Zeroconf{deviceId: deviceId, deviceName: deviceName, deviceType: deviceType}
 	z.reqsChan = make(chan NewUserRequest)
 
@@ -54,7 +54,7 @@ func NewZeroconf(deviceName, deviceId string, deviceType devicespb.DeviceType) (
 		return nil, fmt.Errorf("failed initializing diffiehellman: %w", err)
 	}
 
-	z.listener, err = net.Listen("tcp", "0.0.0.0:0")
+	z.listener, err = net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", port))
 	if err != nil {
 		return nil, fmt.Errorf("failed starting zeroconf listener: %w", err)
 	}