typo (cd -> cb)

lib/nat-traversal.js

@@ -81,7 +81,7 @@ function NatTraversal () {
 
 NatTraversal.prototype.portMapping = function (port, protocol, cb) {
   var self = this
-  if (self._destroyed) return typeof cd === 'function' && cb()
+  if (self._destroyed) return typeof c === 'function' && cb()
   if (typeof protocol === 'function') {
     cb = protocol
     protocol = 'tcp'
@@ -107,7 +107,7 @@ NatTraversal.prototype.portMapping = function (port, protocol, cb) {
 
 NatTraversal.prototype.portUnMapping = function (port, cb) {
   var self = this
-  if (self._destroyed) return typeof cd === 'function' && cb()
+  if (self._destroyed) return typeof cb === 'function' && cb()
   arrayRemove(self._openedPorts, self._openedPorts.findIndex(o => o.port === port))
 
   // Clear intervals