Are there any caveats when using HttpClient with IL2CPP?

About 50% of the time, the library I am working on freezes on a certain network call that is making use of HttpClient.SendAsync(). I am working on getting a smaller test case to submit, but this problem only happens on Unity iOS (Mono2x has different problems with EXC_BAD_ACCESS at the moment so cannot confirm if it works there or not, but on Standalone this works fine). When I pause to get the thread stack traces I notice a similar pattern each time:

1) There are two threads labeled Async I/O Thread that are both blocking on socket receive functionality.
2) I have one thread of my own blocking on receiving data from a hanging HTTP connection (this is on purpose)
3) No other threads go through any of my code, which suggests that the problem is between SendAsync and ContinueWith

Before I get an actual reproduction case ready, is there anything anyone can think of that could be causing this? Does IL2CPP hard limit to two HTTP connections the way that Mono does by default? Can this be altered?

Thanks!

 

I have probably similar issue with IL2CPP and Unity 2019.1.0f2. Some await HttpClient.SendAsync() works and some get stuck. Probably the problem is when await HttpClient.SendAsync() is called from non-main thread, i.e. without Unity SynchronizationContext. The process (window) cannot be closed, probably waiting for SendAsync() to finish.
I'll try to isolate the issue to some example project.

 

So the bug is the FileStream(useAsync:true), not the HttpClient. I have filled the bug https://fogbugz.unity3d.com/default.asp?1156384_t1ec5ls4mtugdoag

 

Another problem is, that the

HttpClient

ignores Windows proxy settings. I have found a workaround for the Mono build:

Code (CSharp):

1. var handler = new HttpClientHandler();
2. handler.UseDefaultCredentials = true;
3. handler.Proxy = System.Net.WebRequest.DefaultWebProxy;
4. var client = new HttpClient(handler);

But it does not work for IL2CPP! I have filled a bug https://fogbugz.unity3d.com/default.asp?1156595_buha3p1v4iq7vpv9

 

Another difference is in the

ServicePointManager.DefaultConnectionLimit = 2

for the Mono build, but 10 for the IL2CPP build.

DefaultConnectionLimit == 10

should be for server ASP.NET, not a desktop app, see https://docs.microsoft.com/cs-cz/dotnet/api/system.net.servicepointmanager.defaultconnectionlimit Anyway, Unity should have same settings regardless of chosen build.

I have filled a bug https://fogbugz.unity3d.com/default.asp?1156607_n5mttn2knh0s3fh1