Update embedded app debugging workflow

scripts/SerialWebConsoleHost.cs

@@ -29,6 +29,7 @@ namespace EmbeddedAppPcDebug
         private readonly object _logLock = new object();
         private readonly object _stateLock = new object();
         private readonly Dictionary<string, DateTime> _webClients = new Dictionary<string, DateTime>(StringComparer.Ordinal);
+        private readonly Dictionary<string, HttpListenerResponse> _liveWebClients = new Dictionary<string, HttpListenerResponse>(StringComparer.Ordinal);
 
         private HttpListener _listener;
         private FileStream _rawStream;
@@ -122,6 +123,8 @@ namespace EmbeddedAppPcDebug
                     _rawPath));
 
                 _listener = new HttpListener();
+                // 必须收到页面连接断开的写异常，不能吞掉后把已关闭的页面永久计为在线。
+                _listener.IgnoreWriteExceptions = false;
                 _listener.Prefixes.Add(_listenPrefix);
                 _listener.Start();
 
@@ -269,6 +272,7 @@ namespace EmbeddedAppPcDebug
             if (string.IsNullOrWhiteSpace(clientId) || clientId.Length > 128) return;
             lock (_stateLock)
             {
+                if (_stopping) return;
                 _webClients[clientId] = DateTime.UtcNow;
                 _hadWebClient = true;
                 _noClientSinceUtc = DateTime.MinValue;
@@ -276,14 +280,76 @@ namespace EmbeddedAppPcDebug
         }
 
         private void RemoveWebClient(string clientId)
+        {
+            RemoveWebClient(clientId, null, "网页主动离页");
+        }
+
+        private void RemoveWebClient(string clientId, HttpListenerResponse expectedResponse, string reason)
         {
             if (string.IsNullOrWhiteSpace(clientId)) return;
+            HttpListenerResponse liveResponse;
+            bool removed;
             lock (_stateLock)
             {
-                _webClients.Remove(clientId);
+                _liveWebClients.TryGetValue(clientId, out liveResponse);
+                // EventSource 重连可能先建立新连接，旧连接的 finally 不能删除新连接。
+                if (expectedResponse != null && !object.ReferenceEquals(liveResponse, expectedResponse)) return;
+                _liveWebClients.Remove(clientId);
+                removed = _webClients.Remove(clientId);
                 if (_hadWebClient && _webClients.Count == 0 && _noClientSinceUtc == DateTime.MinValue)
                     _noClientSinceUtc = DateTime.UtcNow;
             }
+            if (liveResponse != null) { try { liveResponse.Abort(); } catch { } }
+            if (removed && !_stopping) WriteSystemLog(reason + "；客户端 " + clientId);
+        }
+
+        private void SendClientLiveness(HttpListenerContext context)
+        {
+            string clientId = context.Request.QueryString["client"];
+            if (string.IsNullOrWhiteSpace(clientId) || clientId.Length > 128)
+                throw new ArgumentException("页面客户端标识无效。");
+            HttpListenerResponse response = context.Response;
+            HttpListenerResponse previousResponse;
+            lock (_stateLock)
+            {
+                if (_stopping) throw new IOException("串口网页服务正在结束。");
+                _liveWebClients.TryGetValue(clientId, out previousResponse);
+                _liveWebClients[clientId] = response;
+                _webClients[clientId] = DateTime.UtcNow;
+                _hadWebClient = true;
+                _noClientSinceUtc = DateTime.MinValue;
+            }
+            if (previousResponse != null) { try { previousResponse.Abort(); } catch { } }
+
+            try
+            {
+                response.StatusCode = 200;
+                response.ContentType = "text/event-stream; charset=utf-8";
+                response.Headers["Cache-Control"] = "no-store";
+                response.SendChunked = true;
+                byte[] heartbeat = Encoding.UTF8.GetBytes("retry: 500\n: page connection alive\n\n");
+                // 原生 EventSource 持续连接不依赖页面 setInterval。即使页面定时器被节流，
+                // 仍由服务端每秒探测一次连接；页面关闭/崩溃时，写失败后释放该页面租约。
+                while (!_stopping)
+                {
+                    lock (_stateLock)
+                    {
+                        HttpListenerResponse current;
+                        if (!_liveWebClients.TryGetValue(clientId, out current) || !object.ReferenceEquals(current, response)) break;
+                    }
+                    response.OutputStream.Write(heartbeat, 0, heartbeat.Length);
+                    response.OutputStream.Flush();
+                    Thread.Sleep(1000);
+                }
+            }
+            catch (HttpListenerException) { /* 断开的网页连接是正常生命周期事件，不是串口故障。 */ }
+            catch (IOException) { }
+            catch (ObjectDisposedException) { }
+            finally
+            {
+                RemoveWebClient(clientId, response, "网页持续连接已断开（未收到主动离页通知）");
+                try { response.Abort(); } catch { }
+            }
         }
 
         private void WebClientMonitorLoop()
@@ -297,10 +363,14 @@ namespace EmbeddedAppPcDebug
                     List<string> expiredClients = new List<string>();
                     foreach (KeyValuePair<string, DateTime> item in _webClients)
                     {
-                        if ((now - item.Value).TotalSeconds >= WebClientTimeoutSeconds)
+                        if (!_liveWebClients.ContainsKey(item.Key) && (now - item.Value).TotalSeconds >= WebClientTimeoutSeconds)
                             expiredClients.Add(item.Key);
                     }
-                    foreach (string clientId in expiredClients) _webClients.Remove(clientId);
+                    foreach (string clientId in expiredClients)
+                    {
+                        _webClients.Remove(clientId);
+                        WriteSystemLog("网页轮询心跳超时（不能据此断定页面已关闭）；客户端 " + clientId);
+                    }
 
                     if (_webClients.Count > 0)
                     {
@@ -310,13 +380,14 @@ namespace EmbeddedAppPcDebug
                     {
                         if (_noClientSinceUtc == DateTime.MinValue) _noClientSinceUtc = now;
                         shouldStop = (now - _noClientSinceUtc).TotalMilliseconds >= LastClientGraceMilliseconds;
+                        // 判定和置位必须在同一把锁内，防止刷新页面刚接管就被旧判定停止。
+                        if (shouldStop) _stopping = true;
                     }
                 }
 
                 if (shouldStop)
                 {
-                    WriteSystemLog("最后一个串口网页已关闭，正在停止日志采集并释放串口。");
-                    _stopping = true;
+                    WriteSystemLog("所有串口网页连接已结束，宽限期内无页面接管；正在停止日志采集并释放串口。");
                     try { if (_listener != null) _listener.Stop(); } catch { }
                     break;
                 }
@@ -377,6 +448,13 @@ namespace EmbeddedAppPcDebug
                     return;
                 }
 
+                if (method == "GET" && path == "/api/client/live")
+                {
+                    ValidateDisconnectRequest(context);
+                    SendClientLiveness(context);
+                    return;
+                }
+
                 if (method == "GET" && path == "/api/log")
                 {
                     TouchWebClient(context.Request.QueryString["client"]);
@@ -442,7 +520,7 @@ namespace EmbeddedAppPcDebug
 
         private void ValidateDisconnectRequest(HttpListenerContext context)
         {
-            // sendBeacon 无法自定义请求头，因此仅离页通知接口允许在查询参数中携带会话令牌。
+            // sendBeacon / EventSource 无法自定义请求头，仅页面生命周期接口允许查询令牌。
             string token = context.Request.Headers["X-Serial-Token"];
             if (string.IsNullOrWhiteSpace(token)) token = context.Request.QueryString["token"];
             if (!string.Equals(token, _sessionToken, StringComparison.Ordinal))
@@ -503,11 +581,13 @@ namespace EmbeddedAppPcDebug
             string lastError;
             DateTime lastReceive;
             int activeWebClients;
+            int liveWebClients;
             lock (_stateLock)
             {
                 lastError = _lastError;
                 lastReceive = _lastReceiveUtc;
                 activeWebClients = _webClients.Count;
+                liveWebClients = _liveWebClients.Count;
             }
 
             return "{" +
@@ -516,6 +596,7 @@ namespace EmbeddedAppPcDebug
                 "\"receivedBytes\":" + Interlocked.Read(ref _receivedBytes).ToString(CultureInfo.InvariantCulture) + "," +
                 "\"lastReceiveUtc\":\"" + (lastReceive == DateTime.MinValue ? string.Empty : lastReceive.ToString("o", CultureInfo.InvariantCulture)) + "\"," +
                 "\"activeWebClients\":" + activeWebClients.ToString(CultureInfo.InvariantCulture) + "," +
+                "\"liveWebClients\":" + liveWebClients.ToString(CultureInfo.InvariantCulture) + "," +
                 "\"lastError\":\"" + JsonEscape(lastError) + "\"" +
                 "}";
         }
@@ -581,6 +662,14 @@ namespace EmbeddedAppPcDebug
         public void Stop()
         {
             _stopping = true;
+            List<HttpListenerResponse> liveResponses;
+            lock (_stateLock)
+            {
+                liveResponses = new List<HttpListenerResponse>(_liveWebClients.Values);
+                _liveWebClients.Clear();
+                _webClients.Clear();
+            }
+            foreach (HttpListenerResponse response in liveResponses) { try { response.Abort(); } catch { } }
             try { if (_listener != null) _listener.Stop(); } catch { }
             try { if (_serialPort.IsOpen) _serialPort.Close(); } catch { }