I did not know about the long press on stop.
There is a particular location that I can cause this to happen so I will give it a shot.

As far as the sockets getting closed, no I don't think they are being closed properly in some cases. This is likely a framework issue or something goes wrong in the RIL.
They made a lot of RIL changes to properly support LTE so I would not be surprised if there is a problem in there someplace exacerbated by the bad handoffs from LTE to CDMA.

With the leaked radios on this device the situation is improved and I would imagine the reason this has not been sent out as an OTA to this device is because there are more issues they are working on.

is it possible to check the status of the thread that is hung in connect() and kill it?
I suspect that connect() is waiting for an error to be returned but the hardware layer is busy trying to figure itself out.
(yours is not the only application that I have seen hang like this)

I will try to pay special attention to it when it does this to see what it is actually saying on the screen during this hang. I could have sworn it says it's connecting and I know if you hit stop it tries to stop but never actually stops.

I have noticed this issue as well when using the beta internal streaming engine.
I think I know what is going on here..

This device has issues with the radio and handoffs in particular do not work well especially when going from LTE to CDMA/eHRPD.

The internal streaming engine in particular seems to get stuck in a 'connecting' phase when it tries to reconnect.
When you look at dmesg you see stuff like this:
"[MODEM_IF] LTE CRASHED!! LTE DUMP START!!"
Followed by attempts for it to restart the LTE radio and change to the CDMA radio.

I think this is a hardware issue.
After exchanging the device 3 times I finally got one that the LTE radio does not crash on but the handoff between LTE and CDMA is quite poor and often you lose data for over a minute or more before it hands off correctly.

The internal stream engine sits in a hung state for quite some time (over 10 minutes) and I have had to reboot the device to free it up.

There are probably issues in the RIL as well because surely there is some event that is sent when data drops, but I don't know enough about the internals of Android.

I don't know if this helps or not.

Edit: as a sidenote the leaked radios for this device do help with handoffs and data loss and the internal stream engine is not as prone to freezing up.

Also I do not recommend that anyone reading this attempt to root their device and install unofficial updates unless you are willing to accept the consequences of those actions.