From 02f60932ce872ececc98f349c1f9b50ad9facdae Mon Sep 17 00:00:00 2001
From: Stanislav Fifik <standa.fifik@gmail.com>
Date: Sun, 14 Jun 2026 12:47:56 +0200
Subject: [PATCH] feat(probe): add diagnostic probe for mDNS advertisement and
 WebSocket communication

---
 cmd/probe/main.go | 92 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 cmd/probe/main.go

diff --git a/cmd/probe/main.go b/cmd/probe/main.go
new file mode 100644
index 0000000..35e3fd8
--- /dev/null
+++ b/cmd/probe/main.go
@@ -0,0 +1,92 @@
+// Diagnostic probe: advertise _sendspin._tcp via mDNS, listen on /sendspin,
+// and log exactly what the server (Music Assistant) sends after it dials us —
+// WITHOUT sending anything first. Reveals whether MA expects to speak first
+// (role flip) or waits for our client/hello.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/Sendspin/sendspin-go/pkg/discovery"
+	"github.com/gorilla/websocket"
+)
+
+func main() {
+	name := flag.String("name", hostname(), "advertised name")
+	port := flag.Int("port", 8928, "listen + mDNS port")
+	speakFirst := flag.Bool("speak-first", false, "send a server/hello before reading (test role-flip hypothesis)")
+	flag.Parse()
+
+	disc := discovery.NewManager(discovery.Config{ServiceName: *name, Port: *port})
+	if err := disc.Advertise(); err != nil {
+		log.Printf("mdns advertise: %v", err)
+	} else {
+		defer disc.Stop()
+	}
+
+	upgrader := websocket.Upgrader{CheckOrigin: func(*http.Request) bool { return true }}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/sendspin", func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("=== incoming dial from %s (headers: subproto=%q origin=%q UA=%q) ===",
+			r.RemoteAddr, r.Header.Get("Sec-WebSocket-Protocol"), r.Header.Get("Origin"), r.Header.Get("User-Agent"))
+		conn, err := upgrader.Upgrade(w, r, nil)
+		if err != nil {
+			log.Printf("upgrade failed: %v", err)
+			return
+		}
+		defer conn.Close()
+
+		if *speakFirst {
+			hello := `{"type":"server/hello","payload":{"server_id":"probe","name":"probe","version":1,"active_roles":["player@v1"],"connection_reason":"discovery"}}`
+			log.Printf("-> sending server/hello: %s", hello)
+			if err := conn.WriteMessage(websocket.TextMessage, []byte(hello)); err != nil {
+				log.Printf("write failed: %v", err)
+			}
+		}
+
+		log.Printf("listening for first message from server (10s)...")
+		for {
+			conn.SetReadDeadline(time.Now().Add(10 * time.Second))
+			mt, data, err := conn.ReadMessage()
+			if err != nil {
+				log.Printf("read ended: %v", err)
+				if ce, ok := err.(*websocket.CloseError); ok {
+					log.Printf("CLOSE code=%d text=%q", ce.Code, ce.Text)
+				}
+				return
+			}
+			if mt == websocket.BinaryMessage {
+				log.Printf("<- SERVER binary %d bytes", len(data))
+			} else {
+				log.Printf("<- SERVER text: %s", string(data))
+			}
+		}
+	})
+
+	srv := &http.Server{Addr: fmt.Sprintf(":%d", *port), Handler: mux}
+	go func() {
+		log.Printf("probe listening on :%d/sendspin as %q", *port, *name)
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("listen: %v", err)
+		}
+	}()
+
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, os.Interrupt, syscall.SIGTERM)
+	<-sig
+}
+
+func hostname() string {
+	h, _ := os.Hostname()
+	if h == "" {
+		return "sendspin-probe"
+	}
+	return h + "-probe"
+}