DMSG Transport¶

Status	Implemented
Revision	2026-10-27, skywire f37a464a4
Code	`pkg/transport/network/dmsg.go`, `pkg/dmsg`

Abstract¶

The dmsg transport type (tptypes.DMSG) carries a skywire transport over a dmsg stream. It needs no direct route between the two visors. The streams run through dmsg servers, so both visors need a path to each other through the dmsg network. The dmsg protocol is specified in 05-Messaging_System.md.

Overview¶

dmsgClientAdapter wraps the visor's dmsg.Client as a transport Client. Unlike stcpr and sudph, there is no address resolver step. The peer is reached by its public key through the dmsg client's dial procedure, which uses discovery, existing server sessions, server to server forwarding and relays.

Interfaces¶

Method	Behaviour
`Dial(ctx, remote, port)`	`dmsg.Client.DialStream` to `remote:port`.
`Listen(port)`	`dmsg.Client.Listen(port)`.
`Start`	Does nothing. The wrapped client is already serving.
`Close`	Does nothing. The client is shared with other components and closed by its owner.
`PK`, `SK`	The dmsg client's keys.

dmsgTransportAdapter wraps a *dmsg.Stream. It exposes LocalPK, RemotePK, LocalPort, RemotePort and Network (dmsg). Its ConnDetails reports the key of the dmsg server that carries the stream and no remote IP.

Data Formats¶

The dmsg object of the visor configuration is spec.DmsgConfig (pkg/dmsg/dmsgc/spec). The full field list is in 05-Messaging_System.md. A generated configuration sets the following.

{
    "dmsg": {
        "discovery": "dmsg://<dmsg-discovery-pk>:80",
        "sessions_count": 1,
        "servers": [],
        "servers_type": "all",
        "protocol": "yamux"
    }
}

Field	Type	Meaning
`discovery`	string	Discovery address. `discovery_dmsg` holds the `dmsg://` form separately.
`sessions_count`	integer	Server sessions to hold.
`servers`	array of `disc.Entry`	Server entries to use without a discovery lookup. Each entry has `static` (the server key) and `server` (`address`, and optionally `address_ws`, `address_udp` and the other fields of `disc.Server`).
`servers_type`	string	`all`, `official` or `community`. `official` and `community` restrict the sessions to servers whose `serverType` matches.
`protocol`	string	Multiplexer, `yamux` by default.
`carriers`	array of string	Ordered preference from `tcp`, `quic`, `ws`, `wt`.

Behaviour¶

A dmsg stream is end to end encrypted between the two visors, so the server that relays it sees only ciphertext. A stream between visors on different servers is forwarded by one server to a peer server. A visor that holds no server sessions of its own can attach to another visor's dmsg relay and have its streams carried over that visor's sessions (see Relays in 05).

References¶

05 Dmsg
STCPR, SUDPH, STCP