Add support for udp bind port override (3.0.5) Fixes #149

CHANGELOG.md

@@ -1,3 +1,7 @@
+### 3.0.5
+* Add support for `listenUdpPort` to specify a fixed bind port.
+* Improved udp bind failure detection.
+
 ### 3.0.4
 * Add support for Discord widget
 

README.md

@@ -467,25 +467,41 @@ Valheim servers will only respond to queries if they are started in public mode
 For many valve games, additional 'rules' may be fetched into the unstable `raw` field by passing the additional
 option: `requestRules: true`. Beware that this may increase query time.
 
-Important note about Firewalls (replit / docker / some VPS providers)
+Common Issues
 ---
+
+### Firewalls block incoming UDP
+*(replit / docker / some VPS providers)*
+
 Most game query protocols require a UDP request and response. This means that in some environments, gamedig may not be able to receive the reponse required due to environmental restrictions.
 
 Some examples include:
 * Docker containers
-  * You may need to run the container in `--network host` mode so that gamedig can bind a UDP listen port
+  * You may need to run the container in `--network host` mode so that gamedig can bind a UDP listen port.
+  * Alternatively, you can forward a single UDP port to your container, and force gamedig to listen on that port using the
+  instructions in the section down below.
 * replit
   * Most online IDEs run in an isolated container, which will never receive UDP responses from outside networks.
 * Various VPS / server providers
   * Even if your server provider doesn't explicitly block incoming UDP packets, some server hosts block other server hosts from connecting to them for DDOS-mitigation and anti-botting purposes.
 
-Important note about gamedig in the browser
+### Gamedig doesn't work in the browser
----
 Gamedig cannot operate within a browser. This means you cannot package it as part of your webpack / browserify / rollup / parcel package.
 Even if you were able to get it packaged into a bundle, unfortunately no browsers support the UDP protocols required to query server status
 from most game servers. As an alternative, we'd recommend using gamedig on your server-side, then expose your own API to your webapp's frontend
 displaying the status information. If your application is thin (with no constant server component), you may wish to investigate a server-less lambda provider.
 
+### Specifying a listen UDP port override
+In some very rare scenarios, you may need to bind / listen on a fixed local UDP port. The is usually not needed except behind
+some extremely strict firewalls, or within a docker container (where you only wish to forward a single UDP port).
+To use a fixed listen udp port, construct a new Gamedig object like this:
+```
+const gamedig = new Gamedig({
+    listenUdpPort: 13337
+});
+gamedig.query(...)
+```
+
 Usage from Command Line
 ---
 

bin/gamedig.js

@@ -5,7 +5,7 @@ const Minimist = require('minimist'),
 
 const argv = Minimist(process.argv.slice(2), {
     boolean: ['pretty','debug','givenPortOnly'],
-    string: ['guildId']
+    string: ['guildId','listenUdpPort']
 });
 
 const debug = argv.debug;
@@ -41,7 +41,8 @@ if (givenPortOnly) {
     options.givenPortOnly = true;
 }
 
-Gamedig.query(options)
+const gamedig = new Gamedig(options);
+gamedig.query(options)
     .then((state) => {
         if(pretty) {
             console.log(JSON.stringify(state,null,'  '));

lib/GlobalUdpSocket.js

@@ -1,25 +1,29 @@
-const dgram = require('dgram'),
+const dgram = require('dgram');
-    HexUtil = require('./HexUtil'),
+const HexUtil = require('./HexUtil');
-    Logger = require('./Logger');
+const Logger = require('./Logger');
+const util = require('util');
 
 class GlobalUdpSocket {
-    constructor() {
+    constructor({port}) {
         this.socket = null;
         this.callbacks = new Set();
         this.debuggingCallbacks = new Set();
         this.logger = new Logger();
+        this.port = port;
     }
 
-    _getSocket() {
+    async _getSocket() {
         if (!this.socket) {
-            const udpSocket = this.socket = dgram.createSocket('udp4');
+            const udpSocket = dgram.createSocket({
+                type: 'udp4',
+                reuseAddr: true
+            });
             udpSocket.unref();
-            udpSocket.bind();
             udpSocket.on('message', (buffer, rinfo) => {
                 const fromAddress = rinfo.address;
                 const fromPort = rinfo.port;
                 this.logger.debug(log => {
-                    log(fromAddress + ':' + fromPort + " <--UDP");
+                    log(fromAddress + ':' + fromPort + " <--UDP(" + this.port + ")");
                     log(HexUtil.debugDump(buffer));
                 });
                 for (const cb of this.callbacks) {
@@ -29,12 +33,22 @@ class GlobalUdpSocket {
             udpSocket.on('error', e => {
                 this.logger.debug("UDP ERROR:", e);
             });
+            await util.promisify(udpSocket.bind).bind(udpSocket)(this.port);
+            this.port = udpSocket.address().port;
+            this.socket = udpSocket;
         }
         return this.socket;
     }
 
-    send(buffer, address, port) {
+    async send(buffer, address, port, debug) {
-        this._getSocket().send(buffer,0,buffer.length,port,address);
+        const socket = await this._getSocket();
+        if (debug) {
+            this.logger._print(log => {
+                log(address + ':' + port + " UDP(" + this.port + ")-->");
+                log(HexUtil.debugDump(buffer));
+            });
+        }
+        await util.promisify(socket.send).bind(socket)(buffer,0,buffer.length,port,address);
     }
 
     addCallback(callback, debug) {

lib/QueryRunner.js

@@ -9,8 +9,10 @@ const defaultOptions = {
 };
 
 class QueryRunner {
-    constructor() {
+    constructor(runnerOpts = {}) {
-        this.udpSocket = new GlobalUdpSocket();
+        this.udpSocket = new GlobalUdpSocket({
+            port: runnerOpts.listenUdpPort
+        });
         this.gameResolver = new GameResolver();
         this.protocolResolver = new ProtocolResolver();
     }

lib/index.js

@@ -3,8 +3,8 @@ const QueryRunner = require('./QueryRunner');
 let singleton = null;
 
 class Gamedig {
-    constructor() {
+    constructor(runnerOpts) {
-        this.queryRunner = new QueryRunner();
+        this.queryRunner = new QueryRunner(runnerOpts);
     }
 
     async query(userOptions) {

package.json

@@ -24,7 +24,7 @@
     ],
     "main": "lib/index.js",
     "author": "GameDig Contributors",
-    "version": "3.0.4",
+    "version": "3.0.5",
     "repository": {
         "type": "git",
         "url": "https://github.com/gamedig/node-gamedig.git"

protocols/core.js

@@ -252,13 +252,9 @@ class Core extends EventEmitter {
         this.assertValidPort(port);
 
         if(typeof buffer === 'string') buffer = Buffer.from(buffer,'binary');
-        this.debugLog(log => {
-            log(address+':'+port+" UDP-->");
-            log(HexUtil.debugDump(buffer));
-        });
 
         const socket = this.udpSocket;
-        socket.send(buffer, address, port);
+        await socket.send(buffer, address, port, this.options.debug);
 
         if (!onPacket && !onTimeout) {
             return null;