feat: agents connect by WebSocket, falling back to long polling and trying again each minute; auto, ws or lp per machine (0.1.0)

internal/proto/proto.go

@@ -45,6 +45,32 @@ type ControlMessage struct {
 	User      string `json:"user,omitempty"`    // CtrlOpenTerminal: OS user for the shell ("" = the agent's own)
 }
 
+// Transports an agent can reach the server by.
+const (
+	TransportAuto = "auto" // WebSocket, long polling while it cannot connect
+	TransportWS   = "ws"   // WebSocket only
+	TransportLP   = "lp"   // long polling only
+)
+
+// TransportHeader carries the agent's transport setting on poll and config
+// answers.
+const TransportHeader = "X-Transport"
+
+// WSMsg is one message on an agent's WebSocket, either way. Server to agent:
+// "ctrl" (Ctrl, as a control poll would answer), "cfg" (Tunnel and
+// Transport, also a keep-alive), "in" (Frames for session SID), "gone"
+// (session SID is over). Agent to server: "sub" (send the input of session
+// SID here), "out" (Out of session SID).
+type WSMsg struct {
+	T         string          `json:"t"`
+	Ctrl      *ControlMessage `json:"ctrl,omitempty"`
+	SID       string          `json:"sid,omitempty"`
+	Frames    []InFrame       `json:"frames,omitempty"`
+	Out       *OutMessage     `json:"out,omitempty"`
+	Tunnel    string          `json:"tunnel,omitempty"`
+	Transport string          `json:"transport,omitempty"`
+}
+
 // Terminal / stream frame types on the session "in" channel (server -> agent).
 // Reused for both PTY terminals and raw TCP port-forward streams.
 const (