Tutorial: extending the protocol

Because the core names no socket, a new transport is just a pair of functions that move bytes. Seal or frame an outgoing datagram from netchan_send_next() however the medium requires, and hand what arrives to netchan_feed(). The nc_ws transport does exactly this for browsers: it speaks the RFC 6455 WebSocket framing so a browser client reaches an unmodified UDP server. ws_gateway relays between the two, presenting each browser as an ordinary netchan peer.

The address a datagram carries is opaque to the core, so a transport is free to define struct nc_addr however it likes, as long as it packs the bytes on the way in and unpacks them on the way out. A transport that has no meaningful source address, such as a single fixed tunnel, passes NULL and the core copes.

To carry structured messages rather than raw bytes, use the encoding layer below. It needs no change to the core either.