feat: initial commit

probe-server.js

@@ -0,0 +1,26 @@
+'use strict';
+
+const net = require('node:net');
+
+const PORT = Number(process.env.PORT || 19090);
+const HOST = process.env.HOST || '0.0.0.0';
+
+if (Number.isNaN(PORT)) {
+  throw new Error('PORT must be a number');
+}
+
+const server = net.createServer((socket) => {
+  socket.setKeepAlive(true, 15000);
+
+  socket.on('data', (buf) => {
+    const msg = buf.toString('utf8').trim();
+    if (msg === 'ping') {
+      socket.write('pong\n');
+    }
+  });
+});
+
+server.listen(PORT, HOST, () => {
+  console.log(`[probe] listening on ${HOST}:${PORT}`);
+});
+