relay: avoid using Twisted strports

strports aren't ported to py3 yet, so we stick with Endpoints and
Services, which have been.

src/wormhole/servers/relay.py

@@ -1,9 +1,10 @@
 from __future__ import print_function
 import re, json, time, random
 from twisted.python import log
-from twisted.internet import protocol
-from twisted.application import strports, service, internet
+from twisted.internet import reactor, protocol, endpoints
+from twisted.application import service, internet
 from twisted.web import server, static, resource, http
+from ..util.endpoint_service import EndpointServerService
 from .. import __version__
 from ..database import get_db
 
@@ -400,7 +401,8 @@ class RelayServer(service.MultiService):
             welcome["current_version"] = advertise_version
         self.root = Root()
         site = server.Site(self.root)
-        self.relayport_service = strports.service(relayport, site)
+        r = endpoints.serverFromString(reactor, relayport)
+        self.relayport_service = EndpointServerService(r, site)
         self.relayport_service.setServiceParent(self)
         self.relay = Relay(self.db, welcome) # accessible from tests
         self.root.putChild("wormhole-relay", self.relay)
@@ -410,5 +412,6 @@ class RelayServer(service.MultiService):
         if transitport:
             self.transit = Transit()
             self.transit.setServiceParent(self) # for the timer
-            self.transport_service = strports.service(transitport, self.transit)
+            t = endpoints.serverFromString(reactor, transitport)
+            self.transport_service = EndpointServerService(t, self.transit)
             self.transport_service.setServiceParent(self)

src/wormhole/util/endpoint_service.py

@@ -0,0 +1,26 @@
+from twisted.python import log
+from twisted.internet import defer
+from twisted.application import service
+
+# this should probably live in Twisted
+
+class EndpointServerService(service.Service):
+    def __init__(self, endpoint, factory):
+        self.endpoint = endpoint
+        self.factory = factory
+        self._started = defer.Deferred()
+        self._listeningport = None
+
+    def startService(self):
+        d = self.endpoint.listen(self.factory)
+        def _set_port(listeningport):
+            self._listeningport = listeningport
+            self._started.callback(listeningport)
+        d.addCallback(_set_port)
+        d.addErrback(log.err)
+
+    def stopService(self):
+        def _stop(port):
+            return port.stopListening()
+        self._started.addCallback(_stop)
+        return self._started