EXO：使用 EWS 进行流媒体订阅在第三个连接时卡住
我目前正在修改一个解决方案，该解决方案使用对通过 PowerShell 实现的三个房间日历的流式订阅来与 Exchange Online 配合使用。我用 C# 重新实现了它，因为它似乎在 PowerShell 中不起作用（没有通知，也没有错误）。
我正在使用具有模拟权限的应用程序注册来访问日历并通过一个 ExchangeService 连接创建 FreeBusy-Changed 流通知。
对于订阅，我使用三个不同的订阅连接（由于存在三个不同的邮箱）。这是设置每个连接的代码：
var folderIds = new List<FolderId>() { new FolderId(WellKnownFolderName.Calendar, mailbox) };
var subscriptionConnection = new StreamingSubscriptionConnection(exService, 10);
subscriptionConnection.OnNotificationEvent += SubscriptionConnection_OnNotificationEvent;
subscriptionConnection.OnSubscriptionError += SubscriptionConnection_OnSubscriptionError;
subscriptionConnection.OnDisconnect += SubscriptionConnection_OnDisconnect;
var subscription = exService.SubscribeToStreamingNotifications(folderIds, EventType.FreeBusyChanged);
subscriptionConnection.AddSubscription(subscription);
subscriptionConnection.Open();
_subscriptions.Add(subscriptionConnection);
这适用于前两个订阅，但第三个订阅只是挂在方法 SubscribeToStreamingNotifications 上，直到达到超时（10 分钟）。
这不是邮箱本身的问题，因为如果我改变打开连接的顺序，它仍然是第三个。
我知道并发连接数限制为 20 个，但实际上只有 3 个，那么这里有什么问题呢？有什么想法吗？
I'm currently modifying a solution that uses streaming subscriptions to three room calendars implemented via PowerShell to work with Exchange Online. I reimplemented it in C# as it didn't seem to work in PowerShell (no notifications and no error at all).
I am using an app registration with impersonation permissions to access the calendars and create a FreeBusy-Changed streaming notification with one ExchangeService connection.
For the subscriptions I am using three different subscription connections (due to the fact that there are three different mailboxes). This is the code to setup each connection:
var folderIds = new List<FolderId>() { new FolderId(WellKnownFolderName.Calendar, mailbox) };
var subscriptionConnection = new StreamingSubscriptionConnection(exService, 10);
subscriptionConnection.OnNotificationEvent += SubscriptionConnection_OnNotificationEvent;
subscriptionConnection.OnSubscriptionError += SubscriptionConnection_OnSubscriptionError;
subscriptionConnection.OnDisconnect += SubscriptionConnection_OnDisconnect;
var subscription = exService.SubscribeToStreamingNotifications(folderIds, EventType.FreeBusyChanged);
subscriptionConnection.AddSubscription(subscription);
subscriptionConnection.Open();
_subscriptions.Add(subscriptionConnection);
This works for the first two subscriptions, but the third one just hangs there on method SubscribeToStreamingNotifications until the timeout (10mins) is reached.
It's not a problem of the mailbox itself, because if I changed the order I open the connections, it's still the third one.
I know that there is a limit of I think 20 concurrent connections, but these are only three, so what's the problem here? Any ideas?
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问题是，在 .net 中，默认情况下其并发连接数限制为 2 个，请参阅 https://learn.microsoft.com/en-us/dotnet/api/system.net.servicepointmanager.defaultconnectionlimit
因此，您需要将 defaultconnectionlimit 的值设置为27 个并发连接（这是 Office365 中的 EWS 默认并发限制）。例如
The problem is that in .net by default its limited to 2 concurrent connections see https://learn.microsoft.com/en-us/dotnet/api/system.net.servicepointmanager.defaultconnectionlimit
So you need to set the defaultconnectionlimit to value up to 27 concurrent connections (which is the EWS default concurrency limit in Office365). eg