fix: detect port-in-use before starting (#1234)

Add a server error handler in lib/index.js to catch EADDRINUSE and
print a friendly message before the process exits. This approach:
- Works for all startup modes (not just cluster)
- Handles the actual bind failure (no TOCTOU race condition)
- Preserves the synchronous return value of the module export

Also regenerate test root certs with 2048-bit keys (Node.js 25+
rejects 1024-bit keys) and change test wsPort to avoid conflicts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: echopi

lib/index.js

@@ -80,6 +80,14 @@ function proxy(callback) {
       callback.call(server, proxyEvents);
     }
   };
+  server.on('error', function(err) {
+    if (err.code === 'EADDRINUSE') {
+      var addr = (config.host ? config.host + ':' : '') + config.port;
+      console.error('[!] Port ' + addr + ' is already in use.');
+      console.error('[i] Use -p <port> to specify another port.');
+    }
+    throw err;
+  });
   util.getBoundIp(function(host) {
     util.checkPort(!config.INADDR_ANY && !host && config.port, function() {
       server.listen(config.port, host, execCallback);

test/assets/certs/_root.crt

@@ -1,19 +1,24 @@
------BEGIN CERTIFICATE-----
-MIIDBTCCAm6gAwIBAgIBATANBgkqhkiG9w0BAQsFADCBkDEqMCgGA1UEAxMhV0hJ
-U1RMRShhdmVud3VANDg6NDU6MjA6NTI6ZTM6NTEpMQswCQYDVQQGEwJDTjELMAkG
-A1UECBMCWkoxCzAJBgNVBAcTAkhaMSowKAYDVQQKEyFXSElTVExFKGF2ZW53dUA0
-ODo0NToyMDo1MjplMzo1MSkxDzANBgNVBAsTBldQUk9YWTAeFw0xNjA5MDcwODQ0
-MzBaFw0yNjA5MDcwODQ0MzBaMIGQMSowKAYDVQQDEyFXSElTVExFKGF2ZW53dUA0
-ODo0NToyMDo1MjplMzo1MSkxCzAJBgNVBAYTAkNOMQswCQYDVQQIEwJaSjELMAkG
-A1UEBxMCSFoxKjAoBgNVBAoTIVdISVNUTEUoYXZlbnd1QDQ4OjQ1OjIwOjUyOmUz
-OjUxKTEPMA0GA1UECxMGV1BST1hZMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKB
-gQCkl91qX33cnRX3gTTfUi72r8t/D1HavEm0McCaMVDQGJBX0VgVswLNIMGEyAcV
-mSMVleJAgu225M7rtpl9TKzSrOhdHAj7/AjZWOL5GJEuxu0LsuH8ZG9J6sS7HnVO
-//ZGJGjS5gGWk/gAfiII64+gurwasS7xiBHYYZOFTjRARwIDAQABo20wazAMBgNV
-HRMEBTADAQH/MAsGA1UdDwQEAwIC9DA7BgNVHSUENDAyBggrBgEFBQcDAQYIKwYB
-BQUHAwIGCCsGAQUFBwMDBggrBgEFBQcDBAYIKwYBBQUHAwgwEQYJYIZIAYb4QgEB
-BAQDAgD3MA0GCSqGSIb3DQEBCwUAA4GBACv2/Vxc8wa1Cz/qwxJuAUQhQpntGyCN
-UFVJcBr6hHmOKFfs6/l6q8u9bXNKBHeOygn8bn4+u/4qTV040GCm/t4hO1Dx3NhJ
-SKBciStpksJ+kCQp1RvUzNqcmDxkzkVbSXgS+i1BAYezOHsmL5H9fTddZ+q9UtIX
-mN6IvU/hQOj7
------END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIEAzCCAuugAwIBAgIUCKsIACfL/YbRndqWC9mJfoebHwAwDQYJKoZIhvcNAQEL
+BQAwgZAxKjAoBgNVBAMMIVdISVNUTEUoYXZlbnd1QDQ4OjQ1OjIwOjUyOmUzOjUx
+KTELMAkGA1UEBhMCQ04xCzAJBgNVBAgMAlpKMQswCQYDVQQHDAJIWjEqMCgGA1UE
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+83wzhpobL1vNiuM357+PYl7ZE5weOIXNsJKeId371dQOYEBUGe7AJkZCk5KoDPZB
+TAEbJ2bRec3YsPOXCthf20zSop5H9u5qApLkVGt4CKr/V0HAeJgX2S5mJI0G4bG9
+v/u+xotZLa63jxHwpvfZ4zq29XEnCKGJ7PCKrsADk205zApBptgOD4/l3YtHY4m8
+N1NFvGdMargnx9jEAvQWRkRXdsl4wZE=
+-----END CERTIFICATE-----

test/assets/certs/root.key

@@ -1,15 +1,28 @@
------BEGIN RSA PRIVATE KEY-----
-MIICXgIBAAKBgQCkl91qX33cnRX3gTTfUi72r8t/D1HavEm0McCaMVDQGJBX0VgV
-swLNIMGEyAcVmSMVleJAgu225M7rtpl9TKzSrOhdHAj7/AjZWOL5GJEuxu0LsuH8
-ZG9J6sS7HnVO//ZGJGjS5gGWk/gAfiII64+gurwasS7xiBHYYZOFTjRARwIDAQAB
-AoGBAIDuOVJfNQ+AublkrA8XqJQyxtxkGsGWZsHRi0b9xIkOBNvVsANnc5VNyGmD
-6xC/IZ2CCHZyWVXATFqWcguV6XXouF9R8TN+HcEaiZ9epEOnwOSPz4DdEtB+TZp+
-Ih3l/NEzLRNxp7XVqI1k9OG5yguctyzfYcydFem/ZRWcMaxhAkEA0Rb+qGF7jb84
-xRBxFXxnKJVa6C2OSuDG1eecepMcYqNiUTimbk1/3qzJZqXmNBcIAfG/3a5dyM0O
-l1f2xeZ41wJBAMmFOPXkqS4gx8vItUJ36HSgXVOePbdmpBFRWD9R0uj83TuNc3V/
-pD9jKnU/ZQ0DacI57F5zvIxtVy9iAP1iVhECQEJ5sRUPiRyTwxTEGW/fUVzRv0k5
-0pdzx0OSk2lVBB1IHKX+AMvoz9KX1KBR9lJxUBZuKbXtDdwddZogWVCp6ZkCQQC9
-kXcdyPZlEC0ixDHOzyF65Igmass/xWw9ZjoPhpdS2Nv8c3nTZDlL76s3FGWosjdA
-oGB8EX+i0hCb4CNyOJkhAkEADdZsXlSL7e0qy7iE1IP7uHrfse1ZZhIX48DSK+Yg
-nqZ8YdcUsS3RlVOgahqizD723klbKeGq8Pi9t0wHamjHjg==
------END RSA PRIVATE KEY-----
+-----BEGIN PRIVATE KEY-----
+MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDbkpSxOXsMt8CH
+B07l4z9zKbd46tFx1UEKbJFUQikju79AQsF5t08sqygv7dNCQ5TtzgGLXYM9oDTm
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+xw+uUp6C8sYojHg7Ut1qdIY=
+-----END PRIVATE KEY-----

test/config.test.js

@@ -2,7 +2,7 @@
 module.exports = {
   port: 6666,
   serverPort: 8080,
-  wsPort: 8081,
+  wsPort: 18081,
   httpsPort: 5566,
   socksPort: 1080,
   authSocksPort: 1118,