STUN/TURN servers

[Vladimir Panteleev via Digitalmars-d]

On Monday, 28 April 2014 at 18:36:59 UTC, Radu wrote:
> I've seen vibe.d has some pretty nice features when it comes to 
> asynchronous I/O but does someone know of an example of a 
> STUN/TURN server written in it, or in plain D?

Every time I read anything related to STUN/TURN, it becomes 
obvious that these technologies were designed by some committee. 
Metric tons of technical jargon and bureaucratic overhead with an 
absurdly overcomplicated protocol to achieve such a simple thing.

I implemented basic concept behind the TURN server, a TCP relay:

http://worms2d.info/WormNAT2

The protocol is much simpler. As soon as a connection is 
received, it allocates a port and sends it to the client. This is 
the public port allocated for the connection - peers wishing to 
connect to the client can connect to that port on the relay 
server and talk as if they were talking to the client directly. 
Every time a peer connects, the server allocates a temporary port 
for the client to connect to, and sends it over the original 
control connection. After the client connects to said port, they 
can start talking to the peer directly, as if there's no proxy 
in-between. This avoids complicated handshakes, headers, and 
having to modify your protocol and wrap every single packet in a 
stupid header. It's also based on TCP, so you don't have to 
reimplement reordering, retransmission etc. on top of UDP all 
over again.

It's not open-source, and although I could share the source code, 
it's not Vibe'd (D1 in fact). The implementation is very simple, 
though.