UDT: UDP-based Data Transfer Protocol
UDT (UDP-based Data Transfer Protocol) is a transfer protocol on top of UDP. See https://udt.sourceforge.io/ for the original spec and the reference implementation.
This code is a fork from https://github.com/odysseus654/go-udt which itself is a fork.
Stream vs Datagram
// TypeSTREAM describes a reliable streaming protocol (e.g. TCP)
TypeSTREAM SocketType = 1
// TypeDGRAM describes a partially-reliable messaging protocol
TypeDGRAM SocketType = 2
UDT supports both reliable data streaming and partial reliable
messaging. The data streaming semantics is similar to that of TCP,
while the messaging semantics can be regarded as a subset of SCTP
[RFC4960].
From udtSocket.Read:
// for datagram sockets, block until we have a message to return and then return it
// if the buffer isn't big enough, return a truncated message (discarding the rest) and return an error
// for streaming sockets, block until we have at least something to return, then
// fill up the passed buffer as far as we can without blocking again
Deviations
MTU negotiation is disabled. Peernet uses a hardcoded max packet size (see protocol package). Packets may be routed through any network adapter, therefore pinning a MTU specific to a network adapter would not make much sense.
The "rendezvous" functionality has been removed since Peernet supports native Traverse messages for UDP hole punching.
Multiplexing multiple UDT sockets to a single UDT connection is removed. It added complexity without benefits in this case. Peernet uses a single UDP port and UDP connection between two peers. Multiplexing has no effect other than breaking the concept and the security of Peernet message sequences.