Duplicate connections are also detected and handled in AddConnection,
I have not been able to reproduce #182 without the check, so although
it may once have been necessary, it doesn't seem to be needed now.
We did this for symmetry/completeness, but the encoder is actually
"consumed" by handshake() in the creation of the tcp senders, hence it
is in fact dangerous to return it.
We now first exchange a very minimal header, consisting of just the
name of the protocol ("weave") and the min and max version (encoded as
a byte each) we support. This leaves all other details of the
protocol, including the contents of of the handshake, open.
Peers agree to communicate using the maximum mutually supported
version. We record this in the LocalConnection, though atm nothing is
making use of that information.
We set a shorter than normal deadline (10s instead of 60s) for the
header exchange, so we detect version mismatches, garbage, or
non-responsive remotes quickly.
We reset the protocol version to '1' since this is a fresh start; old
weaves will not be able to parse the header.
Closes#871.
When we want a string representation of a Peer, we nearly always just
want the full name. So make String() return that and introduce Info()
to return expanded info.
Since TCP is reliable, we do not need to transmit the nonce itself;
the recipient can simply construct the nonce from its own message
counter. Hence there is no message envelope and we can thus remove a
whole layer of encoding.
David Wragg