Having a very strange issue here...
The built in telnet client in OS X is giving me some strange results. I normally use it for testing whether a TCP connection can be established:
telnet google.com 80
If it's successful, you should expect:
Trying 22.214.171.124... Connected to google.com. Escape character is '^]'.
And from there you can send a HTTP message, or whatever you want to do.
What I'm seeing, which is confusing me to no degree, is connections being connected, regardless of whether it actually was able to connect to the server.
mac:~ user$ telnet 126.96.36.199 12345 Trying 188.8.131.52... Connected to 184.108.40.206. Escape character is '^]'.
220.127.116.11 is obviously not a real server, and there's definitely no service listening on port 12345.
A Wireshark capture confirms that there's not something weird going on. I see TCP syn's go to 18.104.22.168 on 12345, but no response returned.
Note: As I was writing this question, I found the answer, so I'll be posting it shortly.