feat(cat): share the rig over TCI as well as Hamlib — one or the other

internal/rigctld exists because Windows gives a COM port to ONE process: the
moment OpsLog talks to the radio natively, nothing else can. It answers the
programs that speak Hamlib NET rigctl. This answers the ones built around Expert
Electronics' TCI instead — and it answers them whatever radio is connected,
because it sits on the same backend-agnostic Rig interface. An operator with an
Icom or a Yaesu can now hand a TCI-only program a working rig.

One server or the other, never both. They answer the same questions about the
same radio, nothing speaks both, and a second listener is only a second thing to
go wrong.

Written against the official TCI Protocol document (ExpertSDR3/TCI, 12 January
2024, MIT — downloaded and read, not recalled): the initialisation set of §4.1
in its documented order, and the argument order of every command from §4.2. A
client will not proceed past connect without that block, which is why it is
written out in full rather than stubbed.

The one dangerous detail is the VFO mapping. TCI's channel A is where you
LISTEN and channel B where you transmit — the opposite way round from OpsLog's
RigState, which follows ADIF. Getting that backwards would put a station on the
DX's own frequency, so it is pinned in both directions by a test, and RxFreq was
added to the adapter rather than inferred.

Writing channel B while the rig is simplex is ignored: the client asked to
prepare a split transmit frequency, not to QSY, and a logger doing that on every
spot click would drag the operator off the station they were listening to. A
backend that cannot split still refuses out loud.

Only changes are pushed. TCI clients redraw on each command, so re-sending an
unchanged frequency four times a second makes a VFO readout flicker and fights
the operator's own tuning.

Nine tests, no socket needed — the protocol is the decision, not the transport.

app.go

@@ -68,6 +68,7 @@ import (
 	"hamlog/internal/spe"
 	"hamlog/internal/steppir"
 	"hamlog/internal/syncfolder"
+	"hamlog/internal/tciserver"
 	"hamlog/internal/tunergenius"
 	"hamlog/internal/uls"
 	"hamlog/internal/ultrabeam"
@@ -120,6 +121,8 @@ const (
 	keyCATDigitalDefault  = "cat.digital_default" // mode to use when CAT reports DATA
 	keyCATShareEnabled    = "cat.share.enabled"   // expose CAT to other programs (Hamlib NET rigctl)
 	keyCATSharePort       = "cat.share.port"      // TCP port for that server (rigctld default 4532)
+	keyCATShareProto      = "cat.share.proto"     // which sharing server runs: "rigctl" (Hamlib NET) or "tci"
+	keyCATShareTCIPort    = "cat.share.tci_port"  // WebSocket port for the TCI server (TCI default 40001)
 	keyCATXieguPort       = "cat.xiegu.port"      // Xiegu CI-V serial port (G90/X6100…)
 	keyCATXieguBaud       = "cat.xiegu.baud"      // Xiegu CI-V baud (G90 default 19200)
 	keyCATXieguAddr       = "cat.xiegu.addr"      // Xiegu CI-V address (factory 0x70)
@@ -457,8 +460,13 @@ type CATSettings struct {
 	PollMs          int    `json:"poll_ms"`         // poll interval in ms (default 250)
 	DelayMs         int    `json:"delay_ms"`        // pause between commands (default 0)
 	DigitalDefault  string `json:"digital_default"` // when CAT says DATA, surface this mode (FT8/FT4/RTTY/…)
-	ShareEnabled    bool   `json:"share_enabled"`   // serve CAT to other programs (Hamlib NET rigctl)
-	SharePort       int    `json:"share_port"`      // TCP port for it (default 4532)
+	ShareEnabled    bool   `json:"share_enabled"`   // serve CAT to other programs
+	SharePort       int    `json:"share_port"`      // TCP port for the rigctl server (default 4532)
+	// ShareProto picks WHICH server runs — "rigctl" or "tci". One or the other,
+	// not both: they are two ways of asking the same radio the same questions,
+	// and a second listener is only a second thing to go wrong.
+	ShareProto   string `json:"share_proto"`
+	ShareTCIPort int    `json:"share_tci_port"` // WebSocket port for the TCI server (default 40001)
 	// PTT hotkey — a keyboard key that keys the transmitter while OpsLog is
 	// focused (hold-to-talk, or toggle). Uses the configured Audio → PTT method,
 	// falling back to CAT keying when that is VOX/none.
@@ -596,8 +604,12 @@ type App struct {
 	// port: without it, choosing native CAT locks WSJT-X and friends out of the
 	// radio entirely. nil when the operator has not enabled sharing.
 	catShare *rigctld.Server
-	dxcc     *dxcc.Manager
-	cluster  *cluster.Manager
+	// catShareTCI serves the same link to programs built around Expert
+	// Electronics' TCI instead. One or the other runs, never both — they answer
+	// the same questions about the same radio, and nothing speaks both.
+	catShareTCI *tciserver.Server
+	dxcc        *dxcc.Manager
+	cluster     *cluster.Manager
 	// Cluster spots/lines are processed OFF the socket-read goroutine. Enriching a
 	// spot (DXCC/POTA), emitting it to the UI, running alert rules — which can hit
 	// a remote MySQL via isWorkedBandMode — and mirroring it to the Flex all used
@@ -1691,6 +1703,10 @@ func (a *App) shutdown(ctx context.Context) {
 		a.catShare.Stop()
 		a.catShare = nil
 	}
+	if a.catShareTCI != nil {
+		a.catShareTCI.Stop()
+		a.catShareTCI = nil
+	}
 	if a.cat != nil {
 		a.cat.Stop()
 	}
@@ -7449,7 +7465,7 @@ func (a *App) GetCATSettings() (CATSettings, error) {
 	if a.settings == nil {
 		return CATSettings{Backend: "omnirig", OmniRigNum: 1, PollMs: 250}, fmt.Errorf("db not initialized")
 	}
-	m, err := a.settings.GetMany(a.ctx, keyCATEnabled, keyCATBackend, keyCATOmniRigNum, keyCATOmniRigVFO, keyCATFlexHost, keyCATFlexPort, keyCATFlexSpots, keyCATFlexDecodeSpots, keyCATFlexDecodeSecs, keyCATXieguPort, keyCATXieguBaud, keyCATXieguAddr, keyCATXieguPTTLine, keyCATYaesuPort, keyCATYaesuBaud, keyCATKenwoodPort, keyCATKenwoodBaud, keyCATKenwoodHost, keyCATYaesuLowLines, keyCATKenwoodLowLines, keyCATKenwoodDataMode, keyCATIcomPort, keyCATIcomBaud, keyCATIcomAddr, keyCATIcomNetHost, keyCATIcomNetUser, keyCATIcomNetPass, keyCATIcomNetAudio, keyCATTCIHost, keyCATTCIPort, keyCATTCISpots, keyCATPttHotkeyEnabled, keyCATPttHotkey, keyCATPttHotkeyToggle, keyCATPollMs, keyCATDelayMs, keyCATDigitalDefault, keyCATShareEnabled, keyCATSharePort)
+	m, err := a.settings.GetMany(a.ctx, keyCATEnabled, keyCATBackend, keyCATOmniRigNum, keyCATOmniRigVFO, keyCATFlexHost, keyCATFlexPort, keyCATFlexSpots, keyCATFlexDecodeSpots, keyCATFlexDecodeSecs, keyCATXieguPort, keyCATXieguBaud, keyCATXieguAddr, keyCATXieguPTTLine, keyCATYaesuPort, keyCATYaesuBaud, keyCATKenwoodPort, keyCATKenwoodBaud, keyCATKenwoodHost, keyCATYaesuLowLines, keyCATKenwoodLowLines, keyCATKenwoodDataMode, keyCATIcomPort, keyCATIcomBaud, keyCATIcomAddr, keyCATIcomNetHost, keyCATIcomNetUser, keyCATIcomNetPass, keyCATIcomNetAudio, keyCATTCIHost, keyCATTCIPort, keyCATTCISpots, keyCATPttHotkeyEnabled, keyCATPttHotkey, keyCATPttHotkeyToggle, keyCATPollMs, keyCATDelayMs, keyCATDigitalDefault, keyCATShareEnabled, keyCATSharePort, keyCATShareProto, keyCATShareTCIPort)
 	if err != nil {
 		return CATSettings{}, err
 	}
@@ -7491,6 +7507,8 @@ func (a *App) GetCATSettings() (CATSettings, error) {
 		DigitalDefault:   m[keyCATDigitalDefault],
 		ShareEnabled:     m[keyCATShareEnabled] == "1",
 		SharePort:        4532,
+		ShareProto:       "rigctl",
+		ShareTCIPort:     tciserver.DefaultPort,
 	}
 	if n, _ := strconv.Atoi(m[keyCATFlexPort]); n > 0 && n <= 65535 {
 		out.FlexPort = n
@@ -7504,6 +7522,12 @@ func (a *App) GetCATSettings() (CATSettings, error) {
 	if n, _ := strconv.Atoi(m[keyCATSharePort]); n > 0 && n <= 65535 {
 		out.SharePort = n
 	}
+	if p := strings.ToLower(strings.TrimSpace(m[keyCATShareProto])); p == "tci" {
+		out.ShareProto = p
+	}
+	if n, _ := strconv.Atoi(m[keyCATShareTCIPort]); n > 0 && n <= 65535 {
+		out.ShareTCIPort = n
+	}
 	if n, _ := strconv.Atoi(m[keyCATXieguBaud]); n > 0 {
 		out.XieguBaud = n
 	}
@@ -7561,6 +7585,12 @@ func (a *App) SaveCATSettings(s CATSettings) error {
 	if s.SharePort <= 0 || s.SharePort > 65535 {
 		s.SharePort = 4532
 	}
+	if s.ShareProto != "tci" {
+		s.ShareProto = "rigctl"
+	}
+	if s.ShareTCIPort <= 0 || s.ShareTCIPort > 65535 {
+		s.ShareTCIPort = tciserver.DefaultPort
+	}
 	if s.XieguBaud <= 0 {
 		s.XieguBaud = 19200
 	}
@@ -7661,6 +7691,8 @@ func (a *App) SaveCATSettings(s CATSettings) error {
 		keyCATDigitalDefault:   strings.ToUpper(strings.TrimSpace(s.DigitalDefault)),
 		keyCATShareEnabled:     shareEnabled,
 		keyCATSharePort:        strconv.Itoa(s.SharePort),
+		keyCATShareProto:       s.ShareProto,
+		keyCATShareTCIPort:     strconv.Itoa(s.ShareTCIPort),
 	} {
 		if err := a.settings.Set(a.ctx, k, v); err != nil {
 			return err
@@ -18177,6 +18209,18 @@ func (r catShareRig) Split() (bool, int64) {
 	return true, st.FreqHz
 }
 
+// RxFreq is where we LISTEN. Only the TCI server asks for it: TCI's channel A
+// is the receive frequency and channel B the transmit one, the opposite way
+// round from RigState, and a client handed these two the wrong way about would
+// transmit on the DX's own frequency.
+func (r catShareRig) RxFreq() int64 {
+	st := r.a.cat.State()
+	if st.Split && st.RxFreqHz > 0 {
+		return st.RxFreqHz
+	}
+	return st.FreqHz
+}
+
 func (r catShareRig) SetFreq(hz int64) error { return r.a.cat.SetFrequency(hz) }
 func (r catShareRig) SetMode(m string) error { return r.a.cat.SetMode(m) }
 func (r catShareRig) SetPTT(on bool) error   { return r.a.cat.SetPTT(on) }
@@ -18191,17 +18235,35 @@ func (r catShareRig) SetSplit(on bool, txHz int64) error {
 
 // reloadCATShare starts, stops or restarts the sharing server to match the
 // settings. Called from reloadCAT so one "Save & Close" settles both.
+//
+// One server or the other, never both. rigctl and TCI are two ways of asking
+// the same radio the same questions; running both would only double the ways a
+// port clash or a confused client can go wrong, and no program speaks both.
 func (a *App) reloadCATShare(s CATSettings) {
 	want := s.Enabled && s.ShareEnabled
-	// Always tear down first: the port may have changed, and a listener bound to
-	// the old one would keep answering while the client is told to use the new.
+	// Always tear down first: the port — or the protocol — may have changed, and
+	// a listener bound to the old one would keep answering while the client is
+	// told to use the new.
 	if a.catShare != nil {
 		a.catShare.Stop()
 		a.catShare = nil
 	}
+	if a.catShareTCI != nil {
+		a.catShareTCI.Stop()
+		a.catShareTCI = nil
+	}
 	if !want {
 		return
 	}
+	if s.ShareProto == "tci" {
+		srv := tciserver.New(s.ShareTCIPort, catShareRig{a: a}, applog.Printf)
+		if err := srv.Start(); err != nil {
+			applog.Printf("cat share: %v", err)
+			return
+		}
+		a.catShareTCI = srv
+		return
+	}
 	srv := rigctld.New(s.SharePort, catShareRig{a: a}, applog.Printf)
 	if err := srv.Start(); err != nil {
 		// The usual cause is another rigctld — or a previous OpsLog — already on

changelog.json

@@ -3,10 +3,12 @@
     "version": "0.25.8",
     "date": "",
     "en": [
-      "An entity that is a single island group now fills the IOTA reference on its own — no callbook subscription needed."
+      "An entity that is a single island group now fills the IOTA reference on its own — no callbook subscription needed.",
+      "CAT sharing can now speak TCI instead of Hamlib, so a TCI-only program reaches whatever radio OpsLog is on."
     ],
     "fr": [
-      "Une entité qui est un seul groupe d’îles remplit désormais la référence IOTA toute seule, sans abonnement callbook."
+      "Une entité qui est un seul groupe d’îles remplit désormais la référence IOTA toute seule, sans abonnement callbook.",
+      "Le partage CAT peut désormais parler TCI au lieu de Hamlib : un logiciel TCI atteint la radio, quelle qu’elle soit."
     ]
   },
   {

frontend/src/components/SettingsModal.tsx

@@ -1403,7 +1403,7 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
     yaesu_port: '', yaesu_baud: 38400, yaesu_low_lines: false, kenwood_low_lines: false, kenwood_port: '', kenwood_baud: 9600, kenwood_host: '', kenwood_data_mode: 'usb', xiegu_port: '', xiegu_baud: 19200, xiegu_addr: 0x70, xiegu_ptt_line: '',
     icom_port: '', icom_baud: 115200, icom_addr: 0x98, icom_net_host: '', icom_net_user: '', icom_net_pass: '', icom_net_audio: false,
     tci_host: '', tci_port: 40001, tci_spots: false, poll_ms: 250, delay_ms: 0,
-    digital_default: 'FT8', share_enabled: false, share_port: 4532,
+    digital_default: 'FT8', share_enabled: false, share_port: 4532, share_proto: 'rigctl', share_tci_port: 40001,
     ptt_hotkey_enabled: false, ptt_hotkey: '', ptt_hotkey_toggle: false,
   });
   // While true, the next key press is captured as the PTT hotkey.
@@ -3149,15 +3149,47 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
             </label>
             <p className="text-[11px] text-muted-foreground">{t('cat.shareHint')}</p>
             {catCfg.share_enabled && (
-              <div className="space-y-1 max-w-[200px]">
-                <Label>{t('cat.sharePort')}</Label>
-                <PortInput
-                  value={catCfg.share_port || 4532}
-                  fallback={4532}
-                  onChange={(n) => setCatCfg((s) => ({ ...s, share_port: n }))}
-                />
+              <div className="flex flex-wrap items-end gap-4">
+                {/* One protocol or the other. They answer the same questions about
+                    the same radio, and no program speaks both — so this is a
+                    choice, not two switches. */}
+                <div className="space-y-1">
+                  <Label>{t('cat.shareProto')}</Label>
+                  <Select
+                    value={(catCfg as any).share_proto === 'tci' ? 'tci' : 'rigctl'}
+                    onValueChange={(v) => setCatCfg((s) => ({ ...s, share_proto: v } as any))}
+                  >
+                    <SelectTrigger className="h-8 w-[240px]"><SelectValue /></SelectTrigger>
+                    <SelectContent>
+                      <SelectItem value="rigctl">{t('cat.shareRigctl')}</SelectItem>
+                      <SelectItem value="tci">{t('cat.shareTci')}</SelectItem>
+                    </SelectContent>
+                  </Select>
+                </div>
+                <div className="space-y-1 max-w-[200px]">
+                  <Label>{t('cat.sharePort')}</Label>
+                  {(catCfg as any).share_proto === 'tci' ? (
+                    <PortInput
+                      value={(catCfg as any).share_tci_port || 40001}
+                      fallback={40001}
+                      onChange={(n) => setCatCfg((s) => ({ ...s, share_tci_port: n } as any))}
+                    />
+                  ) : (
+                    <PortInput
+                      value={catCfg.share_port || 4532}
+                      fallback={4532}
+                      onChange={(n) => setCatCfg((s) => ({ ...s, share_port: n }))}
+                    />
+                  )}
+                </div>
               </div>
             )}
+            {catCfg.share_enabled && (catCfg as any).share_proto === 'tci' && catCfg.backend === 'tci' && (
+              // Both ends TCI: ExpertSDR is almost certainly already holding
+              // 40001 on this machine, and our server would fail to bind. Worth
+              // saying here rather than leaving it in the log.
+              <p className="text-[11px] text-warning">{t('cat.shareTciClash')}</p>
+            )}
           </div>
           {/* PTT hotkey — a keyboard key that keys the rig while OpsLog is focused.
               Uses the Audio → PTT method (CAT / RTS / DTR), falling back to CAT. */}

frontend/wailsjs/go/models.ts

@@ -2050,6 +2050,8 @@ export namespace main {
 	    digital_default: string;
 	    share_enabled: boolean;
 	    share_port: number;
+	    share_proto: string;
+	    share_tci_port: number;
 	    ptt_hotkey_enabled: boolean;
 	    ptt_hotkey: string;
 	    ptt_hotkey_toggle: boolean;
@@ -2096,6 +2098,8 @@ export namespace main {
 	        this.digital_default = source["digital_default"];
 	        this.share_enabled = source["share_enabled"];
 	        this.share_port = source["share_port"];
+	        this.share_proto = source["share_proto"];
+	        this.share_tci_port = source["share_tci_port"];
 	        this.ptt_hotkey_enabled = source["ptt_hotkey_enabled"];
 	        this.ptt_hotkey = source["ptt_hotkey"];
 	        this.ptt_hotkey_toggle = source["ptt_hotkey_toggle"];

internal/tciserver/tciserver.go

@@ -0,0 +1,521 @@
+// Package tciserver shares OpsLog's CAT link with programs that speak TCI.
+//
+// It is the second half of internal/rigctld, and exists for the same reason:
+// Windows gives a COM port to ONE process, so the moment OpsLog talks to the
+// radio directly nothing else can. rigctld answers the programs that speak
+// Hamlib NET rigctl (WSJT-X, JTDX, MSHV, Log4OM); this answers the ones built
+// around Expert Electronics' TCI instead — and it answers them whatever radio
+// is actually connected, because it sits on the same backend-agnostic
+// interface. An operator with an Icom or a Yaesu can hand a TCI-only program a
+// working rig.
+//
+// ── The protocol ──────────────────────────────────────────────────────────
+// Text commands over a WebSocket, "name:arg,arg;", the same syntax in both
+// directions. On connection the server sends a block of initialisation
+// commands describing the device, ending with ready; and start;. Thereafter
+// either side may send a control command, and the server echoes every change
+// to all connected clients so they stay in step with each other.
+//
+//	vfo:0,0,14074000;      receiver 0, channel A (RX), Hz
+//	vfo:0,1,14080000;      channel B — the TX frequency when split is on
+//	modulation:0,usb;      mode
+//	trx:0,true;            PTT
+//	split_enable:0,true;   split
+//	vfo:0,0;               a READ: the reply is the three-argument form
+//
+// Written against the official TCI Protocol document (ExpertSDR3/TCI, 12
+// January 2024, MIT) — the initialisation set and the argument order of every
+// command below are from §4.1 and §4.2, not from guesswork about what a client
+// might accept.
+package tciserver
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+// Rig is what the server needs from OpsLog's CAT manager. An interface, so this
+// package stays testable without a radio and without importing internal/cat —
+// which also keeps it building on every platform.
+type Rig interface {
+	Freq() int64          // TX frequency in Hz (ADIF sense), 0 if unknown
+	RxFreq() int64        // RX frequency in Hz; equals Freq when not split
+	Mode() string         // ADIF mode (SSB, CW, FT8…)
+	Split() (bool, int64) // split on?, and the TX frequency
+	SetFreq(hz int64) error
+	SetMode(mode string) error
+	SetPTT(on bool) error
+	SetSplit(on bool, txHz int64) error
+}
+
+// DefaultPort is TCI's own default, which is what a client offers first.
+const DefaultPort = 40001
+
+// pollInterval is how often the rig is compared with what the clients were last
+// told. TCI is an event protocol — a client is entitled to sit silent and be
+// told when something moves — so this is the rate at which a knob turned on the
+// radio reaches it.
+const pollInterval = 250 * time.Millisecond
+
+type Server struct {
+	port int
+	rig  Rig
+	log  func(string, ...any)
+
+	mu     sync.Mutex
+	ln     net.Listener
+	http   *http.Server
+	conns  map[*client]struct{}
+	closed bool
+
+	// last is what the clients have been told, so only changes are sent. TCI
+	// clients redraw on every command they receive; re-sending an unchanged
+	// frequency four times a second makes a VFO readout flicker and, in some
+	// clients, fights the operator's own tuning.
+	last state
+}
+
+// state is the part of the rig the clients are kept in step with.
+type state struct {
+	rxHz  int64
+	txHz  int64
+	mode  string
+	split bool
+	valid bool
+}
+
+// client is one connected program.
+type client struct {
+	conn *websocket.Conn
+	mu   sync.Mutex // one writer at a time: gorilla panics on concurrent writes
+}
+
+func (c *client) send(s string) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.conn == nil {
+		return nil // a client with no socket: the tests exercise the protocol, not the transport
+	}
+	_ = c.conn.SetWriteDeadline(time.Now().Add(3 * time.Second))
+	return c.conn.WriteMessage(websocket.TextMessage, []byte(s))
+}
+
+func New(port int, rig Rig, logf func(string, ...any)) *Server {
+	if port <= 0 || port > 65535 {
+		port = DefaultPort
+	}
+	if logf == nil {
+		logf = func(string, ...any) {}
+	}
+	return &Server{port: port, rig: rig, log: logf, conns: map[*client]struct{}{}}
+}
+
+// Start binds the port and serves until Stop.
+func (s *Server) Start() error {
+	ln, err := net.Listen("tcp", fmt.Sprintf(":%d", s.port))
+	if err != nil {
+		return fmt.Errorf("tci server: port %d: %w", s.port, err)
+	}
+	up := websocket.Upgrader{
+		// Any origin: the clients are desktop programs on the same machine or
+		// LAN, and they send whatever Origin their toolkit happens to set. This
+		// is the same trust boundary as the rigctl server on 4532 — a plain TCP
+		// port with no authentication, which is what every logger expects.
+		CheckOrigin: func(*http.Request) bool { return true },
+	}
+	mux := http.NewServeMux()
+	// Any path: clients connect to ws://host:port/ but some append a name.
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		conn, err := up.Upgrade(w, r, nil)
+		if err != nil {
+			s.log("tci server: upgrade from %s failed: %v", r.RemoteAddr, err)
+			return
+		}
+		s.serve(&client{conn: conn}, r.RemoteAddr)
+	})
+	srv := &http.Server{Handler: mux}
+	s.mu.Lock()
+	s.ln, s.http, s.closed = ln, srv, false
+	s.mu.Unlock()
+	go func() { _ = srv.Serve(ln) }()
+	go s.pushLoop()
+	s.log("tci server: listening on :%d", s.port)
+	return nil
+}
+
+// Stop closes the listener and every client.
+func (s *Server) Stop() {
+	s.mu.Lock()
+	if s.closed {
+		s.mu.Unlock()
+		return
+	}
+	s.closed = true
+	ln, srv := s.ln, s.http
+	conns := make([]*client, 0, len(s.conns))
+	for c := range s.conns {
+		conns = append(conns, c)
+	}
+	s.conns = map[*client]struct{}{}
+	s.last = state{}
+	s.mu.Unlock()
+	for _, c := range conns {
+		_ = c.conn.Close()
+	}
+	if srv != nil {
+		_ = srv.Close()
+	}
+	if ln != nil {
+		_ = ln.Close()
+	}
+	s.log("tci server: stopped")
+}
+
+// Clients reports how many programs are connected — the one thing an operator
+// wants to know when a client says it cannot find the rig.
+func (s *Server) Clients() int {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return len(s.conns)
+}
+
+// serve runs one connection: the initialisation block, then commands until it
+// closes.
+func (s *Server) serve(c *client, remote string) {
+	s.mu.Lock()
+	if s.closed {
+		s.mu.Unlock()
+		_ = c.conn.Close()
+		return
+	}
+	s.conns[c] = struct{}{}
+	s.mu.Unlock()
+	s.log("tci server: %s connected", remote)
+
+	for _, line := range s.initBlock() {
+		if err := c.send(line); err != nil {
+			break
+		}
+	}
+	for {
+		_, data, err := c.conn.ReadMessage()
+		if err != nil {
+			break
+		}
+		// One frame may carry several ";"-terminated commands.
+		for _, cmd := range strings.Split(string(data), ";") {
+			if cmd = strings.TrimSpace(cmd); cmd != "" {
+				s.handle(c, cmd)
+			}
+		}
+	}
+	s.mu.Lock()
+	delete(s.conns, c)
+	s.mu.Unlock()
+	_ = c.conn.Close()
+	s.log("tci server: %s disconnected", remote)
+}
+
+// initBlock is the initialisation set from §4.1 of the protocol document, in
+// the documented order, followed by the current state so a client that has just
+// connected shows the right frequency instead of waiting for the first change.
+//
+// A client will not proceed without these: they are how it learns the device
+// exists, what it can do, and that the server has finished setting up.
+func (s *Server) initBlock() []string {
+	rx, tx, mode, split := s.read()
+	return []string{
+		"protocol:ExpertSDR3,1.9;",
+		"device:OpsLog;",
+		"receive_only:false;",
+		"trx_count:1;",
+		"channel_count:2;",
+		// The whole HF/VHF/UHF span OpsLog itself works over. A client uses this
+		// to bound its own tuning; too narrow a range and it refuses to follow the
+		// rig onto 2 m.
+		"vfo_limits:10000,470000000;",
+		"if_limits:-48000,48000;",
+		"modulations_list:am,sam,dsb,lsb,usb,cw,nfm,digl,digu;",
+		"ready;",
+		"start;",
+		fmt.Sprintf("vfo:0,0,%d;", rx),
+		fmt.Sprintf("vfo:0,1,%d;", tx),
+		fmt.Sprintf("modulation:0,%s;", mode),
+		fmt.Sprintf("split_enable:0,%t;", split),
+		"trx:0,false;",
+	}
+}
+
+// read takes one consistent snapshot of the rig in TCI's terms: channel A is
+// where we LISTEN and channel B where we transmit, which is the opposite way
+// round from ADIF's RigState and the one mistake here that would make a client
+// transmit on the DX's frequency.
+func (s *Server) read() (rxHz, txHz int64, mode string, split bool) {
+	split, txHz = s.rig.Split()
+	rxHz = s.rig.RxFreq()
+	if !split {
+		txHz = s.rig.Freq()
+		if rxHz == 0 {
+			rxHz = txHz
+		}
+	}
+	if rxHz == 0 {
+		rxHz = s.rig.Freq()
+	}
+	if txHz == 0 {
+		txHz = rxHz
+	}
+	mode = adifToTCIMode(s.rig.Mode(), rxHz)
+	return rxHz, txHz, mode, split
+}
+
+// pushLoop tells the clients what has changed on the radio.
+func (s *Server) pushLoop() {
+	t := time.NewTicker(pollInterval)
+	defer t.Stop()
+	for range t.C {
+		s.mu.Lock()
+		done := s.closed
+		s.mu.Unlock()
+		if done {
+			return
+		}
+		s.publish()
+	}
+}
+
+// publish sends only what moved. Returns the lines sent, for the tests.
+func (s *Server) publish() []string {
+	rx, tx, mode, split := s.read()
+	cur := state{rxHz: rx, txHz: tx, mode: mode, split: split, valid: true}
+
+	s.mu.Lock()
+	prev := s.last
+	s.last = cur
+	s.mu.Unlock()
+
+	var lines []string
+	if !prev.valid || prev.rxHz != cur.rxHz {
+		lines = append(lines, fmt.Sprintf("vfo:0,0,%d;", cur.rxHz))
+	}
+	if !prev.valid || prev.txHz != cur.txHz {
+		lines = append(lines, fmt.Sprintf("vfo:0,1,%d;", cur.txHz))
+	}
+	if (!prev.valid || prev.mode != cur.mode) && cur.mode != "" {
+		lines = append(lines, fmt.Sprintf("modulation:0,%s;", cur.mode))
+	}
+	if !prev.valid || prev.split != cur.split {
+		lines = append(lines, fmt.Sprintf("split_enable:0,%t;", cur.split))
+	}
+	for _, l := range lines {
+		s.broadcast(l)
+	}
+	return lines
+}
+
+func (s *Server) broadcast(line string) {
+	s.mu.Lock()
+	conns := make([]*client, 0, len(s.conns))
+	for c := range s.conns {
+		conns = append(conns, c)
+	}
+	s.mu.Unlock()
+	for _, c := range conns {
+		_ = c.send(line)
+	}
+}
+
+// handle answers one command from a client. Returns what was sent back, which
+// is "" for a command that only acts on the radio.
+//
+// A command that SETS something is echoed to every client, not just answered to
+// the one that sent it: the protocol document is explicit that the server
+// synchronises all connected clients, and two loggers that disagree about the
+// frequency are worse than one that is merely slow.
+func (s *Server) handle(c *client, cmd string) string {
+	name, args := cmd, ""
+	if i := strings.IndexByte(cmd, ':'); i >= 0 {
+		name, args = cmd[:i], cmd[i+1:]
+	}
+	f := strings.Split(args, ",")
+	arg := func(i int) string {
+		if i < len(f) {
+			return strings.TrimSpace(f[i])
+		}
+		return ""
+	}
+	num := func(i int) int64 {
+		v, _ := strconv.ParseInt(arg(i), 10, 64)
+		return v
+	}
+	reply := func(line string) string {
+		_ = c.send(line)
+		return line
+	}
+	rx, tx, mode, split := s.read()
+
+	switch strings.ToLower(strings.TrimSpace(name)) {
+	case "vfo":
+		// Read form: two arguments. Set form: three.
+		if len(f) < 3 || arg(2) == "" {
+			if arg(1) == "1" {
+				return reply(fmt.Sprintf("vfo:0,1,%d;", tx))
+			}
+			return reply(fmt.Sprintf("vfo:0,0,%d;", rx))
+		}
+		hz := num(2)
+		if hz <= 0 {
+			return ""
+		}
+		if arg(1) == "1" {
+			// Channel B is the transmit frequency, and it only means anything
+			// with split armed. Setting it while simplex would silently move the
+			// rig's only VFO — the client asked to prepare a split TX frequency,
+			// not to QSY.
+			if !split {
+				return ""
+			}
+			if err := s.rig.SetSplit(true, hz); err != nil {
+				s.log("tci server: split TX %d Hz refused: %v", hz, err)
+				return ""
+			}
+		} else if err := s.rig.SetFreq(hz); err != nil {
+			s.log("tci server: tune to %d Hz refused: %v", hz, err)
+			return ""
+		}
+		s.broadcast(fmt.Sprintf("vfo:0,%s,%d;", orZero(arg(1)), hz))
+		return ""
+
+	case "modulation":
+		if len(f) < 2 || arg(1) == "" {
+			return reply(fmt.Sprintf("modulation:0,%s;", mode))
+		}
+		m := tciModeToADIF(arg(1))
+		if m == "" {
+			return ""
+		}
+		if err := s.rig.SetMode(m); err != nil {
+			s.log("tci server: mode %s refused: %v", m, err)
+			return ""
+		}
+		s.broadcast(fmt.Sprintf("modulation:0,%s;", strings.ToLower(arg(1))))
+		return ""
+
+	case "trx":
+		if len(f) < 2 || arg(1) == "" {
+			return reply("trx:0,false;")
+		}
+		on := strings.EqualFold(arg(1), "true")
+		if err := s.rig.SetPTT(on); err != nil {
+			s.log("tci server: PTT %v refused: %v", on, err)
+			return ""
+		}
+		s.broadcast(fmt.Sprintf("trx:0,%t;", on))
+		return ""
+
+	case "split_enable":
+		if len(f) < 2 || arg(1) == "" {
+			return reply(fmt.Sprintf("split_enable:0,%t;", split))
+		}
+		on := strings.EqualFold(arg(1), "true")
+		if err := s.rig.SetSplit(on, tx); err != nil {
+			// The refusal is the useful part: a backend that cannot split says
+			// so, and the client can tell the operator instead of transmitting
+			// on the wrong frequency believing all is well.
+			s.log("tci server: split %v refused: %v", on, err)
+			return ""
+		}
+		s.broadcast(fmt.Sprintf("split_enable:0,%t;", on))
+		return ""
+
+	case "dds":
+		// The panorama's centre frequency. OpsLog has no panorama, so it answers
+		// with the receive frequency — which is where a client draws its own.
+		return reply(fmt.Sprintf("dds:0,%d;", rx))
+
+	case "if":
+		// Offset of the tuning filter inside the panorama: zero, since our "dds"
+		// is the receive frequency itself.
+		return reply("if:0,0,0;")
+
+	case "start", "stop", "ready":
+		return ""
+
+	default:
+		// Everything else — audio streams, CW macros, the E-Coder, the
+		// panorama's own settings — belongs to a radio, not to a CAT link.
+		// Silence rather than an error: a client sends these hopefully at
+		// connect, and a refusal it did not ask for reads as a fault.
+		return ""
+	}
+}
+
+func orZero(s string) string {
+	if s == "" {
+		return "0"
+	}
+	return s
+}
+
+// adifToTCIMode maps an ADIF mode to a TCI modulation.
+//
+// SSB carries no sideband, so it is resolved from the frequency the way every
+// operator does: below 10 MHz lower, above it upper. A client told "ssb" would
+// not recognise it — the modulation list is the vocabulary.
+func adifToTCIMode(mode string, hz int64) string {
+	switch strings.ToUpper(strings.TrimSpace(mode)) {
+	case "":
+		return ""
+	case "CW", "CWR":
+		return "cw"
+	case "USB":
+		return "usb"
+	case "LSB":
+		return "lsb"
+	case "SSB":
+		if hz > 0 && hz < 10_000_000 {
+			return "lsb"
+		}
+		return "usb"
+	case "AM":
+		return "am"
+	case "FM", "NFM":
+		return "nfm"
+	case "RTTY":
+		return "digl"
+	}
+	// Everything else is a data mode: FT8, FT4, JT65, PSK31, MSK144, VARA…
+	// TCI has one pair for the whole family, and the sideband follows the same
+	// rule the data modes themselves use — upper, but for the few HF corners
+	// where LSB is conventional the radio is already there.
+	return "digu"
+}
+
+// tciModeToADIF maps a TCI modulation back to an ADIF mode.
+func tciModeToADIF(m string) string {
+	switch strings.ToLower(strings.TrimSpace(m)) {
+	case "cw":
+		return "CW"
+	case "usb":
+		return "USB"
+	case "lsb":
+		return "LSB"
+	case "am", "sam":
+		return "AM"
+	case "nfm", "fm", "wfm":
+		return "FM"
+	case "digl", "digu", "dsb", "drm":
+		// The data family: the mode the operator is actually running (FT8, RTTY)
+		// is chosen in OpsLog, and a client switching to "digital" must not
+		// overwrite it with a guess. DATA is the honest ADIF answer.
+		return "DATA"
+	}
+	return ""
+}

internal/tciserver/tciserver_test.go

@@ -0,0 +1,242 @@
+package tciserver
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+// fakeRig is a radio that remembers what it was told. Everything here is about
+// what OpsLog does with a client's command, so the rig only has to answer and
+// record.
+type fakeRig struct {
+	freq, rxFreq int64
+	mode         string
+	split        bool
+	txHz         int64
+	ptt          bool
+	splitErr     error
+	calls        []string
+}
+
+func (r *fakeRig) Freq() int64          { return r.freq }
+func (r *fakeRig) RxFreq() int64        { return r.rxFreq }
+func (r *fakeRig) Mode() string         { return r.mode }
+func (r *fakeRig) Split() (bool, int64) { return r.split, r.txHz }
+func (r *fakeRig) SetFreq(hz int64) error {
+	r.calls = append(r.calls, fmt.Sprintf("freq=%d", hz))
+	r.freq, r.rxFreq = hz, hz
+	return nil
+}
+func (r *fakeRig) SetMode(m string) error {
+	r.calls = append(r.calls, "mode="+m)
+	r.mode = m
+	return nil
+}
+func (r *fakeRig) SetPTT(on bool) error {
+	r.calls = append(r.calls, fmt.Sprintf("ptt=%v", on))
+	r.ptt = on
+	return nil
+}
+func (r *fakeRig) SetSplit(on bool, txHz int64) error {
+	if r.splitErr != nil {
+		return r.splitErr
+	}
+	r.calls = append(r.calls, fmt.Sprintf("split=%v,%d", on, txHz))
+	r.split, r.txHz = on, txHz
+	return nil
+}
+
+// srv builds a server with no listener — handle() and publish() are the whole
+// protocol, and neither needs a socket.
+func srv(r *fakeRig) *Server { return New(0, r, nil) }
+
+// A client with no connection: send() would need one, so reads are checked
+// through the returned line instead. This is why handle returns what it sent.
+func ask(t *testing.T, s *Server, cmd string) string {
+	t.Helper()
+	return s.handle(&client{}, cmd)
+}
+
+// The initialisation block is what a client needs before it will believe there
+// is a radio at all. Its contents come from §4.1 of the protocol document, and
+// a client that does not see ready; simply waits for ever.
+func TestInitBlockCarriesTheDocumentedInitialisationSet(t *testing.T) {
+	s := srv(&fakeRig{freq: 14074000, rxFreq: 14074000, mode: "USB"})
+	block := strings.Join(s.initBlock(), "")
+	for _, want := range []string{
+		"protocol:ExpertSDR3,", "device:", "receive_only:false;", "trx_count:1;",
+		"channel_count:2;", "vfo_limits:", "if_limits:", "modulations_list:",
+		"ready;", "start;",
+	} {
+		if !strings.Contains(block, want) {
+			t.Errorf("the initialisation block is missing %q — a client would not proceed past connect", want)
+		}
+	}
+	// And the current state, so a client that connects mid-session shows the
+	// right frequency instead of waiting for the operator to touch something.
+	if !strings.Contains(block, "vfo:0,0,14074000;") {
+		t.Errorf("no current frequency in the block:\n%s", block)
+	}
+	if !strings.Contains(block, "modulation:0,usb;") {
+		t.Errorf("no current mode in the block:\n%s", block)
+	}
+}
+
+// Channel A is where we LISTEN, channel B where we transmit. Handing these to a
+// client the wrong way round is the one mistake here that puts a station on the
+// DX's own frequency, so it is pinned in both directions.
+func TestSplitPutsTheListeningFrequencyOnChannelA(t *testing.T) {
+	// OpsLog's RigState is ADIF: Freq is the TRANSMIT frequency, RxFreq where we
+	// listen. A DX transmitting on 14025 and listening up 2.
+	r := &fakeRig{freq: 14027000, rxFreq: 14025000, mode: "CW", split: true, txHz: 14027000}
+	s := srv(r)
+	block := strings.Join(s.initBlock(), "")
+	if !strings.Contains(block, "vfo:0,0,14025000;") {
+		t.Errorf("channel A is not the receive frequency:\n%s", block)
+	}
+	if !strings.Contains(block, "vfo:0,1,14027000;") {
+		t.Errorf("channel B is not the transmit frequency:\n%s", block)
+	}
+	if !strings.Contains(block, "split_enable:0,true;") {
+		t.Errorf("split was not announced:\n%s", block)
+	}
+}
+
+// Simplex: both channels report the one frequency, so a client reading either
+// gets the right answer.
+func TestSimplexReportsTheSameFrequencyOnBothChannels(t *testing.T) {
+	s := srv(&fakeRig{freq: 7100000, rxFreq: 7100000, mode: "SSB"})
+	if got := ask(t, s, "vfo:0,0"); got != "vfo:0,0,7100000;" {
+		t.Errorf("read of channel A = %q", got)
+	}
+	if got := ask(t, s, "vfo:0,1"); got != "vfo:0,1,7100000;" {
+		t.Errorf("read of channel B = %q", got)
+	}
+	// 7 MHz is below 10, so SSB is lower sideband — a client told "ssb" would
+	// not recognise it at all, the modulation list is the vocabulary.
+	if got := ask(t, s, "modulation:0"); got != "modulation:0,lsb;" {
+		t.Errorf("read of the mode = %q, want lsb below 10 MHz", got)
+	}
+}
+
+// The client tunes the radio.
+func TestAClientCanTuneAndSetModeAndKey(t *testing.T) {
+	r := &fakeRig{freq: 14074000, rxFreq: 14074000, mode: "USB"}
+	s := srv(r)
+	ask(t, s, "vfo:0,0,14200000")
+	ask(t, s, "modulation:0,cw")
+	ask(t, s, "trx:0,true")
+	ask(t, s, "trx:0,false")
+	want := []string{"freq=14200000", "mode=CW", "ptt=true", "ptt=false"}
+	if strings.Join(r.calls, " ") != strings.Join(want, " ") {
+		t.Errorf("the radio was told %v, want %v", r.calls, want)
+	}
+}
+
+// Channel B is the SPLIT transmit frequency. Writing it while the rig is
+// simplex must not move the only VFO there is: the client asked to prepare a
+// transmit frequency, not to QSY — and a logger that did this on every spot
+// click would drag the operator off the station they were listening to.
+func TestWritingChannelBWhileSimplexLeavesTheRigAlone(t *testing.T) {
+	r := &fakeRig{freq: 14074000, rxFreq: 14074000, mode: "USB"}
+	s := srv(r)
+	ask(t, s, "vfo:0,1,14080000")
+	if len(r.calls) != 0 {
+		t.Errorf("the radio was told %v — a split TX frequency moved a simplex rig", r.calls)
+	}
+	// With split armed it means what it says.
+	r.split, r.txHz = true, 14074000
+	ask(t, s, "vfo:0,1,14080000")
+	if len(r.calls) != 1 || r.calls[0] != "split=true,14080000" {
+		t.Errorf("with split on the radio was told %v, want the new transmit frequency", r.calls)
+	}
+}
+
+// A backend that cannot split says so, and the refusal must not be dressed up
+// as success: the client can then tell the operator to use Fake It, where
+// before it would transmit on the receive frequency believing all was well.
+func TestARefusedSplitIsNotAnnouncedAsDone(t *testing.T) {
+	r := &fakeRig{freq: 14025000, rxFreq: 14025000, mode: "CW", splitErr: fmt.Errorf("this backend cannot split")}
+	s := srv(r)
+	if got := ask(t, s, "split_enable:0,true"); got != "" {
+		t.Errorf("a refused split answered %q", got)
+	}
+	if r.split {
+		t.Error("the rig was recorded as split after the backend refused")
+	}
+}
+
+// Only what moved is sent. TCI clients redraw on every command they receive, so
+// re-sending an unchanged frequency four times a second makes a VFO readout
+// flicker and, in some clients, fights the operator's own tuning.
+func TestOnlyChangesAreSent(t *testing.T) {
+	r := &fakeRig{freq: 14074000, rxFreq: 14074000, mode: "USB"}
+	s := srv(r)
+
+	first := s.publish()
+	if len(first) == 0 {
+		t.Fatal("the first pass sent nothing — a client would never learn the state")
+	}
+	if got := s.publish(); len(got) != 0 {
+		t.Errorf("an unchanged radio produced %v", got)
+	}
+
+	r.freq, r.rxFreq = 14200000, 14200000
+	got := s.publish()
+	if len(got) != 2 || !strings.Contains(strings.Join(got, ""), "14200000") {
+		// Both channels move together on a simplex rig, and both are reported.
+		t.Errorf("after a QSY: %v", got)
+	}
+	if got := s.publish(); len(got) != 0 {
+		t.Errorf("the QSY was re-sent: %v", got)
+	}
+}
+
+// Modes travel both ways, and the data family is the interesting half: a client
+// switching to "digital" must not overwrite the mode the operator chose in
+// OpsLog with a guess at which data mode it was.
+func TestModeMapping(t *testing.T) {
+	up := []struct {
+		adif string
+		hz   int64
+		want string
+	}{
+		{"CW", 14025000, "cw"},
+		{"SSB", 14200000, "usb"},
+		{"SSB", 7100000, "lsb"},
+		{"USB", 7100000, "usb"}, // an explicit sideband is never second-guessed
+		{"FT8", 14074000, "digu"},
+		{"RTTY", 14080000, "digl"},
+		{"AM", 3700000, "am"},
+		{"FM", 145500000, "nfm"},
+		{"", 14074000, ""},
+	}
+	for _, c := range up {
+		if got := adifToTCIMode(c.adif, c.hz); got != c.want {
+			t.Errorf("adifToTCIMode(%q, %d) = %q, want %q", c.adif, c.hz, got, c.want)
+		}
+	}
+	down := map[string]string{
+		"cw": "CW", "usb": "USB", "lsb": "LSB", "am": "AM", "sam": "AM",
+		"nfm": "FM", "digu": "DATA", "digl": "DATA", "": "",
+	}
+	for in, want := range down {
+		if got := tciModeToADIF(in); got != want {
+			t.Errorf("tciModeToADIF(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+// A command for something OpsLog is not — audio streams, CW macros, the
+// panorama's settings — is met with silence rather than an error. A client
+// sends these hopefully at connect, and a refusal it did not ask for reads as a
+// fault with the rig.
+func TestUnknownCommandsAreQuiet(t *testing.T) {
+	s := srv(&fakeRig{freq: 14074000, rxFreq: 14074000, mode: "USB"})
+	for _, cmd := range []string{"audio_start:0", "cw_macros_speed:25", "rx_filter_band:0,-2700,-100", "iq_start:0"} {
+		if got := ask(t, s, cmd); got != "" {
+			t.Errorf("%q answered %q", cmd, got)
+		}
+	}
+}