Blazor集成SignalR出现重连失败问题求助（域环境异常）

问题描述 #

我按照微软官方Blazor+SignalR聊天应用教程开发，严格遵循步骤操作后，在公司域管理的电脑上启动应用，页面加载1秒后出现提示“Attempting to reconnect to the server: 1 of 8”。相同代码在私人笔记本上运行正常，怀疑是防火墙入站规则等限制了SignalR，请问需配置哪些项才能使SignalR正常工作？

浏览器控制台日志 #

[2023-12-04T09:43:37.205Z] Information: Normalizing '_blazor' to 'http://localhost:5183/_blazor'.
blazor.server.js:1 [2023-12-04T09:43:37.220Z] Information: WebSocket connected to ws://localhost:5183/_blazor?id=OC5NGtmY6PBlVjFgd2XvFQ.
blazor.server.js:1 [2023-12-04T09:43:37.281Z] Error: Connection disconnected with error 'Error: Server returned an error on close: Connection closed with an error.'.
log @ blazor.server.js:1
_stopConnection @ blazor.server.js:1
transport.onclose @ blazor.server.js:1
_close @ blazor.server.js:1
stop @ blazor.server.js:1
_stopInternal @ blazor.server.js:1
await in _stopInternal (async)
stop @ blazor.server.js:1
_processIncomingData @ blazor.server.js:1
Ft.connection.onreceive @ blazor.server.js:1
i.onmessage @ blazor.server.js:1
blazor.server.js:1 Uncaught (in promise) Error: Server returned an error on close: Connection closed with an error.
at Ft._processIncomingData (blazor.server.js:1:73086)
at Ft.connection.onreceive (blazor.server.js:1:67009)
at i.onmessage (blazor.server.js:1:51322)
_processIncomingData @ blazor.server.js:1
Ft.connection.onreceive @ blazor.server.js:1
i.onmessage @ blazor.server.js:1
await in i.onmessage (async)
(anonymous) @ blazor.server.js:1
(anonymous) @ blazor.server.js:1
blazor.server.js:1 [2023-12-04T09:43:40.285Z] Information: Normalizing '_blazor' to 'http://localhost:5183/_blazor'.
blazor.server.js:1 [2023-12-04T09:43:40.293Z] Information: WebSocket connected to ws://localhost:5183/_blazor?id=Q31qm6zXFYr5JbBC_hAUSQ.
blazor.server.js:1 [2023-12-04T09:43:40.295Z] Error: Error: Circuit host not initialized.
log @ blazor.server.js:1
attemptPeriodicReconnection @ blazor.server.js:1
await in attemptPeriodicReconnection (async)
Yn @ blazor.server.js:1
onConnectionDown @ blazor.server.js:1
(anonymous) @ blazor.server.js:1
(anonymous) @ blazor.server.js:1
_completeClose @ blazor.server.js:1
_connectionClosed @ blazor.server.js:1
Ft.connection.onclose @ blazor.server.js:1
_stopConnection @ blazor.server.js:1
transport.onclose @ blazor.server.js:1
_close @ blazor.server.js:1
stop @ blazor.server.js:1
_stopInternal @ blazor.server.js:1
await in _stopInternal (async)
stop @ blazor.server.js:1
_processIncomingData @ blazor.server.js:1
Ft.connection.onreceive @ blazor.server.js:1
i.onmessage @ blazor.server.js:1
blazor.server.js:1 [2023-12-04T09:44:01.039Z] Information: Normalizing '_blazor' to 'http://localhost:5183/_blazor'.
blazor.server.js:1 [2023-12-04T09:44:01.046Z] Information: WebSocket connected to ws://localhost:5183/_blazor?id=Kno305ikrIy_wQvu9FFrvw.
blazor.server.js:1 [2023-12-04T09:44:01.048Z] Error: Error: Circuit host not initialized.

需配置的项 #

1. 防火墙入站规则 #

• 允许应用使用的端口（示例中为5183）的TCP流量，覆盖WebSocket（ws://）和HTTP协议
• 若后续启用HTTPS，需同步允许对应端口的TLS流量

2. 域组策略与安全软件放行 #

• 确认公司域组策略未阻止本地WebSocket连接（部分域策略会限制localhost的WebSocket通信）
• 检查终端安全软件（如EDR、企业防火墙）是否拦截了Blazor Server的_blazor端点通信，需将该端点加入放行列表

3. SignalR传输方式兼容配置 #

在项目中显式配置多传输方式，避免单一传输被拦截：

• 服务端配置（Program.cs）：

  builder.Services.AddServerSideBlazor()
      .AddHubOptions(options =>
      {
          options.MaximumReceiveMessageSize = 1024 * 1024;
          options.EnableDetailedErrors = true;
      })
      .AddCircuitOptions(options =>
      {
          options.DetailedErrors = true;
      });
  

• 客户端配置（_Host.cshtml）：强制指定 fallback 传输方式

  <script src="_framework/blazor.server.js" autostart="false"></script>
  <script>
    Blazor.start({
      configureSignalR: function (builder) {
        builder.withUrl('/_blazor', {
          transport: signalR.HttpTransportType.WebSockets | signalR.HttpTransportType.LongPolling
        });
      }
    });
  </script>
  

4. 本地环回地址放行 #

确保公司域策略未限制localhost或127.0.0.1的通信，部分域环境会阻止本地环回的WebSocket连接，需将本地环回地址加入信任列表

内容的提问来源于stack exchange，提问作者mrmarco