add option to specify the network interface ip

README.md

@@ -63,6 +63,21 @@ var server = new e131.Server([universes], [port]);
 ```
 
 The `universes` argument can be an array (for joining multiple universes) or a single integer for joining a single universe. If `universes` is omitted, a single value of `1` is assumed. If `port` is omitted, the default E1.31 port `5568` is used.
+
+or 
+
+```javascript
+var e131 = require('e131');
+var server = new e131.Server({
+  universes: [universes], // Multiple universes
+  // universe: universe, // Single universe
+  port: 5568,
+  ip: '192.168.1.12' // IP of the network interface
+});
+```
+
+All options are optional. Use either `universes` or `universe` but not both. The `ip` option is required when more than one network interface is present.
+
 The server will join the corresponding Multicast groups for each provided universe automatically and starts listening as soon as it is created.
 The server performs basic out-of-order detection on received packets. If an out-of-order packet is received, it is discarded.
 

lib/server.js

@@ -32,11 +32,20 @@ function Server(universes, port) {
   }
   EventEmitter.call(this);
 
-  if (universes !== undefined && !Array.isArray(universes)) {
-    universes = [universes];
+  if (Object.prototype.toString.call(universes) === '[object Object]') {
+    var options = universes;
+    this.universes = options.universes || [options.universe] || [0x01];
+    this.port = options.port || e131.DEFAULT_PORT;
+    this.ip = options.ip;
+  } else {
+    if (universes !== undefined && !Array.isArray(universes)) {
+      universes = [universes];
+    }
+
+    this.universes = universes || [0x01];
+    this.port = port || e131.DEFAULT_PORT;
   }
-  this.universes = universes || [0x01];
-  this.port = port || e131.DEFAULT_PORT;
+
   this._socket = dgram.createSocket('udp4');
   this._lastSequenceNumber = 0;
 
@@ -67,7 +76,12 @@ function Server(universes, port) {
   this._socket.bind(this.port, function onListening() {
     self.universes.forEach(function (universe) {
       var multicastGroup = e131.getMulticastGroup(universe);
-      self._socket.addMembership(multicastGroup);
+
+      if (this.ip) {
+        self._socket.addMembership(multicastGroup, this.ip);
+      } else {
+        self._socket.addMembership(multicastGroup);
+      }
     });
   });
 }