Added a MinecraftServer.lookup method, converts a string to host/port (including SRV lookup)

This closes #12

mcstatus/server.py

@@ -1,6 +1,7 @@
 from mcstatus.pinger import ServerPinger
 from mcstatus.protocol.connection import TCPSocketConnection, UDPSocketConnection
 from mcstatus.querier import ServerQuerier
+import dns.resolver
 
 
 class MinecraftServer:
@@ -8,6 +9,29 @@ class MinecraftServer:
         self.host = host
         self.port = port
 
+    @staticmethod
+    def lookup(address):
+        host = address
+        port = None
+        if ":" in address:
+            parts = address.split(":")
+            if len(parts) > 2:
+                raise ValueError("Invalid address '%s'" % address)
+            host = parts[0]
+            port = int(parts[1])
+        if port is None:
+            port = 25565
+            try:
+                answers = dns.resolver.query("_minecraft._tcp." + host, "SRV")
+                if len(answers):
+                    answer = answers[0]
+                    host = str(answer.target).rstrip(".")
+                    port = int(answer.port)
+            except Exception:
+                pass
+
+        return MinecraftServer(host, port)
+
     def ping(self, retries=3, **kwargs):
         attempt = 0
         connection = TCPSocketConnection((self.host, self.port))

mcstatus/tests/test_server.py

@@ -81,4 +81,42 @@ class TestMinecraftServer(TestCase):
             with patch("mcstatus.server.ServerQuerier") as querier:
                 querier.side_effect = [Exception, Exception, Exception]
                 self.assertRaises(Exception, self.server.query)
-                self.assertEqual(querier.call_count, 3)
+                self.assertEqual(querier.call_count, 3)
+
+    def test_by_address_no_srv(self):
+        with patch("dns.resolver.query") as query:
+            query.return_value = []
+            self.server = MinecraftServer.lookup("example.org")
+            query.assert_called_once_with("_minecraft._tcp.example.org", "SRV")
+        self.assertEqual(self.server.host, "example.org")
+        self.assertEqual(self.server.port, 25565)
+
+    def test_by_address_invalid_srv(self):
+        with patch("dns.resolver.query") as query:
+            query.side_effect = [Exception]
+            self.server = MinecraftServer.lookup("example.org")
+            query.assert_called_once_with("_minecraft._tcp.example.org", "SRV")
+        self.assertEqual(self.server.host, "example.org")
+        self.assertEqual(self.server.port, 25565)
+
+    def test_by_address_with_srv(self):
+        with patch("dns.resolver.query") as query:
+            answer = Mock()
+            answer.target = "different.example.org."
+            answer.port = 12345
+            query.return_value = [answer]
+            self.server = MinecraftServer.lookup("example.org")
+            query.assert_called_once_with("_minecraft._tcp.example.org", "SRV")
+        self.assertEqual(self.server.host, "different.example.org")
+        self.assertEqual(self.server.port, 12345)
+
+    def test_by_address_with_port(self):
+        self.server = MinecraftServer.lookup("example.org:12345")
+        self.assertEqual(self.server.host, "example.org")
+        self.assertEqual(self.server.port, 12345)
+
+    def test_by_address_with_multiple_ports(self):
+        self.assertRaises(ValueError, MinecraftServer.lookup, "example.org:12345:6789")
+
+    def test_by_address_with_invalid_port(self):
+        self.assertRaises(ValueError, MinecraftServer.lookup, "example.org:port")