test(wstracker-probe): standalone Go binary to verify WSS tracker reachability

Tiny `go run ./cmd/wstracker-probe` that spins up an anacrolix/torrent
Client with WebRTC enabled, advertises a random info_hash to the given
WSS tracker, and reports via Callbacks.StatusUpdated whether the
announce round-trip succeeded.

Used as the production smoke for unarr ↔ wss://tracker.torrentclaw.com:

  $ /tmp/wstracker-probe -tracker wss://tracker.torrentclaw.com -timeout 30s
  [probe] tracker=wss://tracker.torrentclaw.com info_hash=e978df8d... timeout=30s
  [probe] tracker connected: wss://tracker.torrentclaw.com
  [probe] tracker announce OK: wss://tracker.torrentclaw.com ih=e978df8d...
  [probe] OK — tracker announce succeeded

Disables TCP/uTP/DHT/IPv6/UPnP — only the WS tracker path matters here.
Exit codes: 0 success, 1 announce error, 2 timeout.

cmd/wstracker-probe/main.go

@@ -0,0 +1,117 @@
+// wstracker-probe — connects to a WebSocket BitTorrent tracker, advertises
+// a fake info_hash, and reports whether the announce succeeds.
+//
+// Usage:
+//
+//	go run ./cmd/wstracker-probe -tracker wss://tracker.torrentclaw.com
+//
+// Exit code 0 on TrackerAnnounceSuccessful, 1 on timeout/error.
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	alog "github.com/anacrolix/log"
+	"github.com/anacrolix/torrent"
+	"github.com/anacrolix/torrent/storage"
+	"github.com/pion/webrtc/v4"
+)
+
+func main() {
+	tracker := flag.String("tracker", "wss://tracker.torrentclaw.com", "WSS tracker URL to probe")
+	timeout := flag.Duration("timeout", 30*time.Second, "max wait for successful announce")
+	flag.Parse()
+
+	tmp, err := os.MkdirTemp("", "wstracker-probe-*")
+	if err != nil {
+		log.Fatalf("temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmp)
+
+	cfg := torrent.NewDefaultClientConfig()
+	cfg.DataDir = tmp
+	cfg.DefaultStorage = storage.NewMMap(tmp)
+	cfg.Seed = false
+	cfg.NoUpload = false
+	cfg.DisableTCP = true
+	cfg.DisableUTP = true
+	cfg.DisableIPv6 = true
+	cfg.NoDHT = true
+	cfg.NoDefaultPortForwarding = true
+	cfg.ListenPort = 0
+	cfg.Logger = alog.Default.FilterLevel(alog.Critical)
+	cfg.DisableWebtorrent = false
+	cfg.ICEServerList = []webrtc.ICEServer{
+		{URLs: []string{"stun:stun.l.google.com:19302"}},
+	}
+
+	annSuccess := make(chan struct{}, 1)
+	annError := make(chan error, 1)
+	cfg.Callbacks.StatusUpdated = append(
+		cfg.Callbacks.StatusUpdated,
+		func(e torrent.StatusUpdatedEvent) {
+			switch e.Event { //nolint:exhaustive // peer events are noise for tracker probe
+			case torrent.TrackerConnected:
+				if e.Error != nil {
+					fmt.Printf("[probe] tracker connect FAILED: %v\n", e.Error)
+				} else {
+					fmt.Printf("[probe] tracker connected: %s\n", e.Url)
+				}
+			case torrent.TrackerAnnounceSuccessful:
+				fmt.Printf("[probe] tracker announce OK: %s ih=%s\n", e.Url, e.InfoHash)
+				select {
+				case annSuccess <- struct{}{}:
+				default:
+				}
+			case torrent.TrackerAnnounceError:
+				fmt.Printf("[probe] tracker announce ERROR: %s ih=%s err=%v\n", e.Url, e.InfoHash, e.Error)
+				select {
+				case annError <- e.Error:
+				default:
+				}
+			case torrent.TrackerDisconnected:
+				fmt.Printf("[probe] tracker disconnected: %s err=%v\n", e.Url, e.Error)
+			}
+		},
+	)
+
+	client, err := torrent.NewClient(cfg)
+	if err != nil {
+		log.Fatalf("create torrent client: %v", err)
+	}
+	defer client.Close()
+
+	var ih [20]byte
+	if _, err := rand.Read(ih[:]); err != nil {
+		log.Fatalf("random info_hash: %v", err)
+	}
+	magnet := fmt.Sprintf("magnet:?xt=urn:btih:%x&tr=%s", ih, *tracker)
+	fmt.Printf("[probe] tracker=%s info_hash=%x timeout=%s\n", *tracker, ih, *timeout)
+
+	t, err := client.AddMagnet(magnet)
+	if err != nil {
+		log.Fatalf("add magnet: %v", err)
+	}
+	defer t.Drop()
+
+	ctx, cancel := context.WithTimeout(context.Background(), *timeout)
+	defer cancel()
+
+	select {
+	case <-annSuccess:
+		fmt.Println("[probe] OK — tracker announce succeeded")
+		os.Exit(0)
+	case err := <-annError:
+		fmt.Printf("[probe] FAIL — tracker announce error: %v\n", err)
+		os.Exit(1)
+	case <-ctx.Done():
+		fmt.Printf("[probe] FAIL — timeout after %s\n", *timeout)
+		os.Exit(2)
+	}
+}