Add DisplayGet packet debug test

Standalone test script to verify DisplayGet packet format matches
MCP client implementation. Useful for debugging protocol issues.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/client-test.mjs

@@ -0,0 +1,139 @@
+#!/usr/bin/env node
+/**
+ * Test the ViceClient directly by importing from the bundled dist
+ */
+
+import { Socket } from "net";
+
+const HOST = "127.0.0.1";
+const PORT = 6502;
+
+const STX = 0x02;
+const API_VERSION = 0x02;
+const CMD_DISPLAY_GET = 0x84;
+
+let requestId = 0;
+let socket;
+let responseBuffer = Buffer.alloc(0);
+
+function nextRequestId() {
+  requestId = (requestId + 1) & 0xffffffff;
+  return requestId;
+}
+
+function buildPacket(command, body) {
+  // Same format as MCP client: 11-byte header
+  const header = Buffer.alloc(11);
+  header[0] = STX;
+  header[1] = API_VERSION;
+  header.writeUInt32LE(body.length, 2);
+  header.writeUInt32LE(nextRequestId(), 6);
+  header[10] = command;
+  return Buffer.concat([header, body]);
+}
+
+async function connect() {
+  return new Promise((resolve, reject) => {
+    socket = new Socket();
+    socket.on("connect", resolve);
+    socket.on("error", reject);
+    socket.connect(PORT, HOST);
+  });
+}
+
+async function sendDisplayGet() {
+  return new Promise((resolve, reject) => {
+    // Body: useVicii(1) + format(1) - exactly like MCP client.getDisplay()
+    const body = Buffer.alloc(2);
+    body[0] = 1; // useVicii = true
+    body[1] = 0; // format = indexed 8-bit
+
+    const packet = buildPacket(CMD_DISPLAY_GET, body);
+    const reqId = requestId;
+
+    console.log(`Sending DisplayGet, reqId=${reqId}`);
+    console.log(`Packet (${packet.length} bytes): ${packet.toString("hex")}`);
+
+    const timeout = setTimeout(() => {
+      reject(new Error("Timeout waiting for DisplayGet response"));
+    }, 15000);
+
+    const handleData = () => {
+      while (responseBuffer.length >= 12) {
+        if (responseBuffer[0] !== STX) {
+          responseBuffer = responseBuffer.subarray(1);
+          continue;
+        }
+
+        const bodyLength = responseBuffer.readUInt32LE(2);
+        const totalLength = 12 + bodyLength;
+
+        if (responseBuffer.length < totalLength) {
+          console.log(`Waiting for more data: have ${responseBuffer.length}, need ${totalLength}`);
+          break;
+        }
+
+        const responseType = responseBuffer[6];
+        const errorCode = responseBuffer[7];
+        const respReqId = responseBuffer.readUInt32LE(8);
+        const respBody = responseBuffer.subarray(12, totalLength);
+
+        console.log(`Got response: type=0x${responseType.toString(16)}, error=0x${errorCode.toString(16)}, reqId=${respReqId}, bodyLen=${respBody.length}`);
+
+        responseBuffer = responseBuffer.subarray(totalLength);
+
+        // Skip async events
+        if (respReqId === 0xffffffff) {
+          console.log(`  (async event, skipping)`);
+          continue;
+        }
+
+        if (respReqId === reqId) {
+          clearTimeout(timeout);
+          socket.off("data", onData);
+          resolve({ responseType, errorCode, body: respBody });
+          return;
+        }
+      }
+    };
+
+    const onData = (data) => {
+      console.log(`Received ${data.length} bytes`);
+      responseBuffer = Buffer.concat([responseBuffer, data]);
+      handleData();
+    };
+
+    socket.on("data", onData);
+    socket.write(packet);
+  });
+}
+
+async function main() {
+  console.log("Testing DisplayGet with MCP client packet format...\n");
+
+  console.log("1. Connecting...");
+  await connect();
+  console.log("   Connected!\n");
+
+  console.log("2. Sending DisplayGet...");
+  try {
+    const resp = await sendDisplayGet();
+    if (resp.errorCode !== 0) {
+      console.log(`   ERROR: 0x${resp.errorCode.toString(16)}`);
+    } else {
+      const width = resp.body.readUInt16LE(4);
+      const height = resp.body.readUInt16LE(6);
+      const bufferLength = resp.body.readUInt32LE(17);
+      console.log(`   SUCCESS! ${width}x${height}, ${bufferLength} bytes`);
+    }
+  } catch (err) {
+    console.log(`   FAILED: ${err.message}`);
+  }
+
+  socket.end();
+}
+
+main().catch(err => {
+  console.error("Fatal:", err);
+  process.exit(1);
+});