diff --git a/src/allmydata/test/common.py b/src/allmydata/test/common.py
index fa032ec..e8117bf 100644
--- a/src/allmydata/test/common.py
+++ b/src/allmydata/test/common.py
@@ -503,14 +503,10 @@ class SystemTestMixin(pollmixin.PollMixin, testutil.StallMixin):
         def _connected(res):
             log.msg("CONNECTED")
             # now find out where the web port was
-            l = self.clients[0].getServiceNamed("webish").listener
-            port = l._port.getHost().port
-            self.webish_url = "http://localhost:%d/" % port
+            self.webish_url = self.clients[0].getServiceNamed("webish").getURL()
             if self.numclients >=4:
                 # and the helper-using webport
-                l = self.clients[3].getServiceNamed("webish").listener
-                port = l._port.getHost().port
-                self.helper_webish_url = "http://localhost:%d/" % port
+                self.helper_webish_url = self.clients[3].getServiceNamed("webish").getURL()
         d.addCallback(_connected)
         return d
 
@@ -541,9 +537,7 @@ class SystemTestMixin(pollmixin.PollMixin, testutil.StallMixin):
         def _maybe_get_webport(res):
             if num == 0:
                 # now find out where the web port was
-                l = self.clients[0].getServiceNamed("webish").listener
-                port = l._port.getHost().port
-                self.webish_url = "http://localhost:%d/" % port
+                self.webish_url = self.clients[0].getServiceNamed("webish").getURL()
         d.addCallback(_maybe_get_webport)
         return d
 
diff --git a/src/allmydata/test/no_network.py b/src/allmydata/test/no_network.py
index f19ad68..554a75f 100644
--- a/src/allmydata/test/no_network.py
+++ b/src/allmydata/test/no_network.py
@@ -287,10 +287,10 @@ class GridTestMixin:
                                num_servers=num_servers,
                                client_config_hooks=client_config_hooks)
         self.g.setServiceParent(self.s)
-        self.client_webports = [c.getServiceNamed("webish").listener._port.getHost().port
+        self.client_webports = [c.getServiceNamed("webish").getPortnum()
+                                for c in self.g.clients]
+        self.client_baseurls = [c.getServiceNamed("webish").getURL()
                                 for c in self.g.clients]
-        self.client_baseurls = ["http://localhost:%d/" % p
-                                for p in self.client_webports]
 
     def get_clientdir(self, i=0):
         return self.g.clients[i].basedir
diff --git a/src/allmydata/test/test_web.py b/src/allmydata/test/test_web.py
index f68e98d..615429c 100644
--- a/src/allmydata/test/test_web.py
+++ b/src/allmydata/test/test_web.py
@@ -169,8 +169,10 @@ class WebMixin(object):
         self.ws = webish.WebishServer(self.s, "0", staticdir=self.staticdir,
                                       clock=self.clock)
         self.ws.setServiceParent(self.s)
-        self.webish_port = port = self.ws.listener._port.getHost().port
-        self.webish_url = "http://localhost:%d" % port
+        self.webish_port = self.ws.getPortnum()
+        self.webish_url = self.ws.getURL()
+        assert self.webish_url.endswith("/")
+        self.webish_url = self.webish_url[:-1] # these tests add their own /
 
         l = [ self.s.create_dirnode() for x in range(6) ]
         d = defer.DeferredList(l)
diff --git a/src/allmydata/webish.py b/src/allmydata/webish.py
index 2cd77aa..d9f24c4 100644
--- a/src/allmydata/webish.py
+++ b/src/allmydata/webish.py
@@ -1,4 +1,4 @@
-import time
+import re, time
 from twisted.application import service, strports, internet
 from twisted.web import http
 from twisted.internet import defer
@@ -149,30 +149,65 @@ class WebishServer(service.MultiService):
         self.site.remember(MyExceptionHandler(), inevow.ICanHandleException)
         if staticdir:
             self.root.putChild("static", static.File(staticdir))
+        if re.search(r'^\d', webport):
+            webport = "tcp:"+webport # twisted warns about bare "0" or "3456"
         s = strports.service(webport, site)
         s.setServiceParent(self)
+
+        self._scheme = None
+        self._portnum = None
+        self._url = None
         self.listener = s # stash it so the tests can query for the portnum
+
         self._started = defer.Deferred()
         if nodeurl_path:
             self._started.addCallback(self._write_nodeurl_file, nodeurl_path)
 
+    def getURL(self):
+        assert self._url
+        return self._url
+    def getPortnum(self):
+        assert self._portnum
+        return self._portnum
+
     def startService(self):
-        service.MultiService.startService(self)
-        self._started.callback(None)
+        def _got_port(lp):
+            self._portnum = lp.getHost().port
+            # what is our webport?
+            assert self._scheme
+            self._url = "%s://127.0.0.1:%d/" % (self._scheme, self._portnum)
+            self._started.callback(None)
+            return lp
+        def _fail(f):
+            self._started.errback(f)
+            return f
 
-    def _write_nodeurl_file(self, junk, nodeurl_path):
-        # what is our webport?
+        service.MultiService.startService(self)
         s = self.listener
-        if isinstance(s, internet.TCPServer):
-            base_url = "http://127.0.0.1:%d/" % s._port.getHost().port
+        if hasattr(s, 'endpoint') and hasattr(s, '_waitingForPort'):
+            # Twisted 10.2 gives us a StreamServerEndpointService. This is
+            # ugly but should do for now.
+            classname = s.endpoint.__class__.__name__
+            self._scheme = (classname.startswith('SSL')) and 'https' or 'http'
+            s._waitingForPort.addCallbacks(_got_port, _fail)
+        elif isinstance(s, internet.TCPServer):
+            # Twisted <= 10.1
+            self._scheme = 'http'
+            _got_port(s._port)
         elif isinstance(s, internet.SSLServer):
-            base_url = "https://127.0.0.1:%d/" % s._port.getHost().port
+            # Twisted <= 10.1
+            self._scheme = 'https'
+            _got_port(s._port)
         else:
-            base_url = None
-        if base_url:
+            # who knows, probably some weirdo future version of Twisted
+            self._started.errback(AssertionError("couldn't find out the scheme or port for the web-API server"))
+
+
+    def _write_nodeurl_file(self, junk, nodeurl_path):
+        if self._url:
             f = open(nodeurl_path, 'wb')
             # this file is world-readable
-            f.write(base_url + "\n")
+            f.write(self._url + "\n")
             f.close()
 
 class IntroducerWebishServer(WebishServer):
