feat: replace serial automation with resident TCP agent

.qemu/tcp-agent-relay.mjs

@@ -0,0 +1,71 @@
+import net from "node:net";
+
+const HOST = "127.0.0.1";
+const TOOL_PORT = 5555;
+const OBSERVER_PORT = 5557;
+const TCP_AGENT_PORT = 5558;
+
+let tcpAgent = null;
+let controller = null;
+const observers = new Set();
+
+function safeWrite(socket, data) {
+  if (socket && !socket.destroyed && socket.writable) socket.write(data);
+}
+
+function trace(source, data) {
+  const text = data.toString("ascii");
+  const shortened = text.length > 400 ? `${text.slice(0, 400)}…` : text;
+  for (const observer of observers) safeWrite(observer, `${source} ${shortened}\r\n`);
+}
+
+const tcpAgentServer = net.createServer((socket) => {
+  if (tcpAgent && !tcpAgent.destroyed) {
+    socket.end();
+    return;
+  }
+  tcpAgent = socket;
+  socket.setNoDelay(true);
+  socket.on("data", (data) => {
+    safeWrite(controller, data);
+    trace("DOS->Pi", data);
+  });
+  socket.on("close", () => {
+    if (tcpAgent === socket) tcpAgent = null;
+  });
+  socket.on("error", () => {});
+});
+
+const toolServer = net.createServer((socket) => {
+  if (controller && !controller.destroyed) {
+    socket.end("ERR 544350204147454E5420434F4E54524F4C4C45522042555359\r\n");
+    return;
+  }
+  if (!tcpAgent || tcpAgent.destroyed) {
+    socket.end("ERR 544350204147454E54204E4F5420434F4E4E4543544544\r\n");
+    return;
+  }
+  controller = socket;
+  socket.setNoDelay(true);
+  socket.on("data", (data) => {
+    safeWrite(tcpAgent, data);
+    trace("Pi->DOS", data);
+  });
+  socket.on("close", () => {
+    if (controller === socket) controller = null;
+  });
+  socket.on("error", () => {});
+});
+
+const observerServer = net.createServer((socket) => {
+  observers.add(socket);
+  socket.setNoDelay(true);
+  socket.write("DOS TCP agent observer (read-only)\r\n");
+  socket.on("data", () => {});
+  socket.on("close", () => observers.delete(socket));
+  socket.on("error", () => observers.delete(socket));
+});
+
+tcpAgentServer.listen(TCP_AGENT_PORT, HOST);
+toolServer.listen(TOOL_PORT, HOST);
+observerServer.listen(OBSERVER_PORT, HOST);