Weird socket bug, 'Error #2031: Socket Error'

Question

I'm putting together an application which opens a connection
to a server, sends a chunk of binary data and then closes the
connection. When I run the application without handing
IOEventError, I get the socket error message below but the data
sends. When I handle IOEventError, I get the same message passed to
the handler but no data is sent. When I capture TCP data during the
connection, you can that without the handler a '[PSH, ACK]' packet
of length 29 (my data) is sent out. With the handler, a '[FIN]'
packet is sent instead. I've pasted the errors, code and TCP
traffic below.
Has anyone else encountered this socket weirdness? How do I
figure out what this error message means?
Thanks for the help!
-J. Flier
Error message to the console with no handler (but data
sends): "Error #2044: Unhandled IOErrorEvent:. text=Error #2031:
Socket Error.
at handleSendPacketClick()[src\Test.mxml:156]
at Test_Button2_click()[\src\Test.mxml:333]"
Error message to the handler (no data sends): "IOErrorEvent
type="ioError" bubbles=false cancelable=false eventPhase=2
text="Error #2031: Socket Error. URL: 192.168.220.128"
errorID=2031"
TCP traffic with no handler:
1 0.000000 192.168.220.1 192.168.220.128 TCP timelot > cbt
[SYN] Seq=0 Win=65535 Len=0 MSS=1460
2 0.000484 192.168.220.128 192.168.220.1 TCP cbt > timelot
[SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1460
3 0.000542 192.168.220.1 192.168.220.128 TCP timelot > cbt
[ACK] Seq=1 Ack=1 Win=65535 Len=0
4 0.005418 192.168.220.1 192.168.220.128 TCP timelot > cbt
[PSH, ACK] Seq=1 Ack=1 Win=65535 Len=29
5 0.005615 192.168.220.128 192.168.220.1 TCP cbt > timelot
[ACK] Seq=1 Ack=30 Win=5840 Len=0
6 2.410136 192.168.220.1 192.168.220.128 TCP timelot > cbt
[FIN, ACK] Seq=30 Ack=1 Win=65535 Len=0
7 2.450241 192.168.220.128 192.168.220.1 TCP cbt > timelot
[ACK] Seq=1 Ack=31 Win=5840 Len=0
8 2.486507 192.168.220.128 192.168.220.1 TCP cbt > timelot
[FIN, ACK] Seq=1 Ack=31 Win=5840 Len=0
9 2.486563 192.168.220.1 192.168.220.128 TCP timelot > cbt
[ACK] Seq=31 Ack=2 Win=65535 Len=0
TCP traffic with handler:
17 438.448287 192.168.220.1 192.168.220.128 TCP dvt-data >
cbt [SYN] Seq=0 Win=65535 Len=0 MSS=1460
18 438.448629 192.168.220.128 192.168.220.1 TCP cbt >
dvt-data [SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1460
19 438.448683 192.168.220.1 192.168.220.128 TCP dvt-data >
cbt [ACK] Seq=1 Ack=1 Win=65535 Len=0
20 438.449489 192.168.220.1 192.168.220.128 TCP dvt-data >
cbt [FIN, ACK] Seq=1 Ack=1 Win=65535 Len=0
21 438.451503 192.168.220.128 192.168.220.1 TCP cbt >
dvt-data [ACK] Seq=1 Ack=2 Win=5840 Len=0
22 438.452759 192.168.220.128 192.168.220.1 TCP cbt >
dvt-data [FIN, ACK] Seq=1 Ack=2 Win=5840 Len=0
23 438.452793 192.168.220.1 192.168.220.128 TCP dvt-data >
cbt [ACK] Seq=2 Ack=2 Win=65535 Len=0
var socket:Socket=new Socket();
// First we generate our packet
msg=generateMessage();
// Then we open a connection
//socket.addEventListener(IOErrorEvent.IO_ERROR, onIOError);
socket.connect(backendIPTextInput.text, int(textInput.text));
// Finally we send the packet
socket.writeBytes(msg);
socket.flush();
socket.close();

Answer 1

Having spent three days trying to run this down, I'm going to start by saying that I'm honestly surprised no ones put together a page that says, "Oh hey, before you use XML sockets here's 150 things you need to know first."  Or maybe someone did put that page together but I couldn't find it.  So in the interest of saving someone the big hassle I just had, here's what you might be doing wrong.
Start here:
http://www.adobe.com/support/flash/action_scripts/actionscript_dictionary/actionscript_dic tionary860.html
Then have a look at this, particularly the example:
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/net/XMLSocket.html
Now you might be tempted to skip all of the adding of those event listeners, but if you do if any kind of communication problem arises in the connection Flash won't know how to handle it and you'll get Error #2031 or #2044 or both.
But wait, that's not all!  You also have to come up with some way to let the PLAYER (not your application, not the sever) know that it's allowed to communicate on the port, and for that you need this document:
http://www.adobe.com/devnet/flashplayer/articles/socket_policy_files.html
Seriously, if this helps you, please let me and Adobe know.