Update with sock index.js

lib/index.js

@@ -43,10 +43,17 @@ class AgiServer extends EventEmitter {
     });
     this.server.on('close', () => this.emit('close'));
     
+    if(this.options.host){
         this.server.listen(this.options.port, this.options.host, () => {
           console.log('agi server on', this.options.port, 'listen');
         });
     }
+    else{
+        this.server.listen(this.options.port, () => {
+          console.log('agi server on', this.options.port, 'listen');
+        });
+    }
+  }
 
   /**
    * @return {Promise}