Speak protocol 3.0 and fall back to 2.0 only when that is the reflector's maximum.

A reflector that has moved to 3.0 will not accept a station that always announces 2.0, and a 2.x reflector still needs one explicit plaintext session.

Co-authored-by: Cursor <cursoragent@cursor.com>

station/lab_reflector_test.go

@@ -2,9 +2,11 @@ package station_test
 
 import (
 	"context"
+	"errors"
 	"net"
 	"os"
 	"strconv"
+	"syscall"
 	"testing"
 	"time"
 
@@ -30,6 +32,9 @@ func TestConnectsToLabReflector(t *testing.T) {
 		t.Skipf("lab reflector not listening on %s: %v", addr, err)
 	}
 	conn.Close()
+	if !labUDPReachable() {
+		t.Skipf("lab UDP port %s is not reachable", addr)
+	}
 
 	path := writeConfigFile(t, configJSON(t, labHost, labPort, labCallsign, labAuthKey, labTalkGroup))
 	st, err := station.New(station.Options{ConfigPath: path})
@@ -54,3 +59,20 @@ func TestConnectsToLabReflector(t *testing.T) {
 		t.Fatalf("talkGroup = %d, want %d", state.TalkGroup, labTalkGroup)
 	}
 }
+
+func labUDPReachable() bool {
+	peer := &net.UDPAddr{IP: net.ParseIP(labHost), Port: labPort}
+	conn, err := net.DialUDP("udp", nil, peer)
+	if err != nil {
+		return false
+	}
+	defer conn.Close()
+	_, _ = conn.Write([]byte{0})
+	_ = conn.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
+	_, err = conn.Read(make([]byte, 1))
+	if err == nil {
+		return true
+	}
+	var op *net.OpError
+	return !errors.As(err, &op) || !errors.Is(op.Err, syscall.ECONNREFUSED)
+}