.NET MAUI应用使用WebSocket抛出WebSocketException异常求助

这段代码在.NET WinForms应用中可正常建立WebSocket连接、发送命令至服务器且服务器能正常接收，但在.NET MAUI中运行时会抛出System.Net.WebSockets.WebSocketException异常，相关代码如下：

private async void BtnOn_Clicked(object sender, EventArgs e)
{
    await SendCommand("O");
}

private async void BtnOff_Clicked(object sender, EventArgs e)
{
    await SendCommand("F");
}

private async Task SendCommand(string command)
{
    ClientWebSocket socket = new ClientWebSocket();

    try
    {
        await socket.ConnectAsync(new Uri("ws://192.168.0.2:80/command"), CancellationToken.None);

        byte[] buffer = Encoding.UTF8.GetBytes(command);
        await socket.SendAsync(new ArraySegment<byte>(buffer), WebSocketMessageType.Text, true, CancellationToken.None);

        Trace.WriteLine("Incoming message: " + command);

        // Receive response if needed
        var responseBuffer = new byte[1024];
        var response = await socket.ReceiveAsync(new ArraySegment<byte>(responseBuffer), CancellationToken.None);
        var responseMessage = Encoding.UTF8.GetString(responseBuffer, 0, response.Count);

    }
    catch (Exception ex)
    {
        await DisplayAlert("Error", $"Error: {ex.Message}", "OK");
    }
    finally
    {
        if (socket.State == WebSocketState.Open || socket.State == WebSocketState.Connecting)
            await socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closed by the client", CancellationToken.None);

        socket.Dispose();
    }
}

可能的原因及解决办法 #

• 网络权限未配置：MAUI是跨平台框架，不同平台需明确配置网络权限
  • Android：在Platforms/Android/AndroidManifest.xml中添加权限

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    

  • iOS：在Platforms/iOS/Info.plist中添加网络访问配置（允许非HTTPS连接）

    <key>NSAppTransportSecurity</key>
    <dict>
        <key>NSExceptionDomains</key>
        <dict>
            <key>192.168.0.2</key>
            <dict>
                <key>NSIncludesSubdomains</key>
                <true/>
                <key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
                <true/>
            </dict>
        </dict>
    </dict>
    

• 无超时的CancellationToken：代码中使用CancellationToken.None，MAUI中建议添加超时Token避免无限等待
  修改连接和发送逻辑：

  using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
  await socket.ConnectAsync(new Uri("ws://192.168.0.2:80/command"), cts.Token);
  

• 连接状态检查缺失：在发送和接收前确认WebSocket状态是否为Open
  在SendAsync前添加：

  if (socket.State != WebSocketState.Open)
  {
      throw new InvalidOperationException("WebSocket连接未处于打开状态");
  }
  

• 原生实现跨平台差异：MAUI中ClientWebSocket底层实现与WinForms不同，可尝试替换为第三方库（如WebSocketSharp-netstandard）简化跨平台兼容问题

内容的提问来源于stack exchange，提问作者Carlos Costa