Default to 127.0.0.1:2375 on Windows

Following the logic of the Docker client.
Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

docker/clientbase.py

 import json
 import struct
+import sys
 
 import requests
 import requests.exceptions
@@ -31,7 +32,7 @@ class ClientBase(requests.Session):
 
         self._auth_configs = auth.load_config()
 
-        base_url = utils.parse_host(base_url)
+        base_url = utils.parse_host(base_url, sys.platform)
         if base_url.startswith('http+unix://'):
             self._custom_adapter = unixconn.UnixAdapter(base_url, timeout)
             self.mount('http+docker://', self._custom_adapter)

docker/utils/utils.py

@@ -272,11 +272,15 @@ def parse_repository_tag(repo):
 # fd:// protocol unsupported (for obvious reasons)
 # Added support for http and https
 # Protocol translation: tcp -> http, unix -> http+unix
-def parse_host(addr):
+def parse_host(addr, platform=None):
     proto = "http+unix"
     host = DEFAULT_HTTP_HOST
     port = None
     path = ''
+
+    if not addr and platform == 'win32':
+        addr = '{0}:{1}'.format(DEFAULT_HTTP_HOST, 2375)
+
     if not addr or addr.strip() == 'unix://':
         return DEFAULT_UNIX_SOCKET
 

tests/utils_test.py

@@ -79,8 +79,6 @@ class UtilsTest(base.BaseTestCase):
             'tcp://:7777': 'http://127.0.0.1:7777',
             'http://:7777': 'http://127.0.0.1:7777',
             'https://kokia.jp:2375': 'https://kokia.jp:2375',
-            '': 'http+unix://var/run/docker.sock',
-            None: 'http+unix://var/run/docker.sock',
             'unix:///var/run/docker.sock': 'http+unix:///var/run/docker.sock',
             'unix://': 'http+unix://var/run/docker.sock',
             'somehost.net:80/service/swarm': (
@@ -90,10 +88,20 @@ class UtilsTest(base.BaseTestCase):
 
         for host in invalid_hosts:
             with pytest.raises(DockerException):
-                parse_host(host)
+                parse_host(host, None)
 
         for host, expected in valid_hosts.items():
-            self.assertEqual(parse_host(host), expected, msg=host)
+            self.assertEqual(parse_host(host, None), expected, msg=host)
+
+    def test_parse_host_empty_value(self):
+        unix_socket = 'http+unix://var/run/docker.sock'
+        tcp_port = 'http://127.0.0.1:2375'
+
+        for val in [None, '']:
+            for platform in ['darwin', 'linux2', None]:
+                assert parse_host(val, platform) == unix_socket
+
+            assert parse_host(val, 'win32') == tcp_port
 
     def test_kwargs_from_env_empty(self):
         os.environ.update(DOCKER_HOST='',