handle case where server returns ip in square brackets

Author: feross

client.js

@@ -513,9 +513,9 @@ Tracker.prototype._handleResponse = function (requestUrl, data) {
     } else if (Array.isArray(data.peers6)) {
       // tracker returned normal response
       data.peers.forEach(function (peer) {
-        var ip = /:/.test(peer.ip) ?
-          '[' + peer.ip + ']' :
-          peer.ip
+        var ip = /^\[/.test(peer.ip)
+          ? peer.ip
+          : '[' + peer.ip + ']'
         self.client.emit('peer', ip + ':' + peer.port)
       })
     }