TCPHandler object helps you
establish TCP connection with remote peer, even wodVPN internally uses
UDP packets.
What it does it basically opens two local listening sockets -
UDP (for wodVPN), and TCP (for remote peer). When packet arrives on
either of those, it relays it to another one. Having local UDP packet is
neccessary for wodVPN. When you set up TCPHandler object, wodVPN will
use this UDP on 127.0.0.1 interface just as all other endpoints received
as result of Search method, and it will try to establish connection
through it. Of course that is one side of TCPHandler. Once local ports
are open (and TCPHandler set to Listen state), you can use it's Connect
method to connect to remote peer if you know remote endpoint.
You can use TCPHandler to make connection through TCP Relay too. TCP
Relay can be easily setup on some port on public computer, visible to
both peers. When TCPHandler connects to TCP Relay, it presents itself,
and searches for remote peer. When remote peer arrives to same relay,
TCP Relay starts relaying TCP packets, which are then related to UDP
packets via TCPHandler. Obviously, this is a bit slower connection than
direct UDP->UDP.
You can establish connections in two basic modes - direct P2P, or
through relay:
1. Direct P2P: wodVPN (UDP) ->
TCPHandler (UDP) ->
TCPHandler (TCP) <----> TCPHandler (TCP)
-> TCPHandler (UDP) ->
wodVPN (UDP)
2. Through relay: wodVPN (UDP) ->
TCPHandler (UDP) ->
TCPHandler (TCP) <--> TCP Relay
<--> TCP Handler (TCP) ->
TCPHandler (UDP) ->
wodVPN (UDP).
Using TCPHandler you can establish connections through most
firewalls, especially if you set TCP Relay on some server on port 443.
