Client bootstrap infinite wait when connecting from server to another server, but connects fine when running client standalone

[Parsee1]

I'm new to Netty, still learning it and trying to make a proxy supporting HTTP/2.

I'm using Http2Tiles as the target server (https://127.0.0.1:8443)
My client bootstrap (MyClient.clientBootStrap) wait infinitely when it's started from my proxy server (Programe.Main), https://192.168.1.98/
Debugging found it hungs at line 81. Console not printing "connected."

But if I change the startup object to MyClient in the project properties and run again, breakpoint hits at line 83 and console prints "connected."

Here's my repo https://github.com/Parsee1/SpanNettyTest1

Besides I rewrote it in java with Netty. -- https://github.com/Parsee1/NettyTest1
Client bootstrap connects fine even when connecting from server. Bam!

Did I do something wrong or is it a CSharp thing? Need some help over here :'(