blind-relay

Blind relay for UDX over Protomux channels. By acting as a blind relay, a host may accept pairing requests from other hosts and relay UDX stream messages between them, similar to Traversal Using Relays around NAT (TURN).

npm i blind-relay

Protocol

sequenceDiagram
    actor a as peer a
    actor r as relay
    actor b as peer b

    par
        a ->> r: pair { isInitiator: true, token, id, seq }
    and
        b ->> r: pair { isInitiator: false, token, id, seq }
    end

    note over r: The relay pairs peers a and b based on the token, allocates a new stream for both peers, and sends back the stream info

    par
        r -->> a: pair { isInitiator: true, token, id, seq }
    and
        r -->> b: pair { isInitiator: false, token, id, seq }
    end

    par
        a ->> r: unpair { token }

        note left of r: The relay deallocates the stream previously allocated to peer a
    and
        b ->> r: unpair { token }

        note right of r: The relay deallocates the stream previously allocated to peer b
    end

Messages

All types are specified as their corresponding compact-encoding codec.

pair (0)

1. bitfield(1) Flags.
   1. isInitiator
2. fixed32 Preexchanged token.
3. uint Stream ID of the sender.
4. uint Initial stream sequence no. of the sender.

unpair (1)

1. bitfield(0) Flags, reserved.
2. fixed32 Preexchanged token.

Stats

Relay servers expose in-memory stats on server.stats.

• sessions.accepted, sessions.opened, sessions.closed, sessions.active
• pairings.requested, pairings.matched, pairings.cancelled, pairings.pending, pairings.active
• streams.opened, streams.closed, streams.errors, streams.active

All counters are cumulative for the lifetime of the process, while active and pending values reflect the current relay state.

License

Apache-2.0