Fixes a bug where an empty bind address (as in SOCKS5 UDP ASSOCIATE) bypassed the SplitHostPort guard and passed `""` to `AddrFeature.ParseFrom`, which returns an error for empty hosts. Default to `0.0.0.0:0` (any address, any port) when address is empty.
When rtcp listener calls Router.Bind with ":8000" (port-only address),
the relay AddrFeature.ParseFrom fails because net.SplitHostPort returns
an empty host. This leaves AType at default 0, causing AddrFeature.Encode
to return ErrBadAddrType.
Fix by normalizing port-only addresses to "0.0.0.0:<port>" in both tunnel
and relay connectors before ParseFrom. Also fix error check on
resp.WriteTo in the tunnel handler's handleBind to prevent silent
protocol desync.
PahaKush
Yuan Tong
ginuerzh