working concept

tunnel/index.mjs

@@ -15,7 +15,8 @@ const DEFAULT_TIMEOUT_MS = 30000;
 const LOCAL_HOST = '127.0.0.1';
 
 function parseArgs() {
-  const args = process.argv.slice(2);
+  // slice(1): when run as a bundled binary, argv is [binaryPath, ...cliArgs]; slice(2) would drop --key
+  const args = process.argv.slice(1);
   let key = null;
   let remotePort = DEFAULT_REMOTE_PORT;
   let localPort = DEFAULT_LOCAL_PORT;
@@ -43,6 +44,42 @@ function emit(line) {
   } catch (_) {}
 }
 
+/**
+ * Verify that the port is accepting TCP connections before we report it.
+ * Tries to connect to host:port; resolves when connect succeeds (then we close the socket).
+ * Rejects on error or after timeoutMs.
+ */
+function waitUntilPortAccepting(host, port, timeoutMs = 10000, intervalMs = 200) {
+  const deadline = Date.now() + timeoutMs;
+  return new Promise((resolve, reject) => {
+    function tryConnect() {
+      if (Date.now() >= deadline) {
+        reject(new Error('Port did not accept connections within ' + timeoutMs + 'ms'));
+        return;
+      }
+      import('net').then((net) => {
+        const socket = net.createConnection(
+          { port, host, allowHalfOpen: false },
+          () => {
+            socket.setTimeout(0);
+            socket.destroy();
+            resolve();
+          }
+        );
+        socket.on('error', () => {
+          socket.destroy();
+          setTimeout(tryConnect, intervalMs);
+        });
+        socket.setTimeout(intervalMs, () => {
+          socket.destroy();
+          setTimeout(tryConnect, intervalMs);
+        });
+      }).catch(reject);
+    }
+    tryConnect();
+  });
+}
+
 async function run() {
   const mod = await import('holesail');
   const Holesail = mod.default || mod;
@@ -70,12 +107,17 @@ async function run() {
       else resolve(port);
     };
 
-    const hs = new Holesail({
+    const opts = {
       client: true,
       key,
       host: LOCAL_HOST,
       port: portToUse
-    });
+    };
+    // If the Holesail API supports remotePort, tell it which port on the peer to use (e.g. 22 for SSH).
+    if (remotePort > 0 && remotePort <= 65535) {
+      opts.remotePort = remotePort;
+    }
+    const hs = new Holesail(opts);
 
     if (typeof hs.on === 'function') {
       hs.on('error', (err) => {
@@ -105,6 +147,8 @@ async function run() {
   try {
     const port = await readyPromise;
     hs = run._hs;
+    // Verify the port is actually accepting connections before reporting it
+    await waitUntilPortAccepting(LOCAL_HOST, port, 10000, 200);
     emit(JSON.stringify({ local_port: port, ready: true }));
   } catch (err) {
     const msg = (err && err.message) ? err.message : String(err);