1 files changed, 101 insertions, 0 deletions
diff --git a/BitTorrent/NatCheck.py b/BitTorrent/NatCheck.py
new file mode 100644
index 0000000..6363ded
--- /dev/null
+++ b/BitTorrent/NatCheck.py
@@ -0,0 +1,101 @@
+# The contents of this file are subject to the BitTorrent Open Source License
+# Version 1.1 (the License).  You may not copy or use this file, in either
+# source code or executable form, except in compliance with the License.  You
+# may obtain a copy of the License at http://www.bittorrent.com/license/.
+#
+# Software distributed under the License is distributed on an AS IS basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the License
+# for the specific language governing rights and limitations under the
+# License.
+
+# Written by Bram Cohen
+
+from cStringIO import StringIO
+from socket import error as socketerror
+
+protocol_name = 'BitTorrent protocol'
+
+# header, reserved, download id, my id, [length, message]
+
+
+class NatCheck(object):
+
+    def __init__(self, resultfunc, downloadid, peerid, ip, port, rawserver):
+        self.resultfunc = resultfunc
+        self.downloadid = downloadid
+        self.peerid = peerid
+        self.ip = ip
+        self.port = port
+        self.closed = False
+        self.buffer = StringIO()
+        self.next_len = 1
+        self.next_func = self.read_header_len
+        rawserver.async_start_connection((ip, port), self)
+
+    def connection_started(self, s):
+        self.connection = s
+        self.connection.write(chr(len(protocol_name)) + protocol_name +
+                              (chr(0) * 8) + self.downloadid)
+
+    def connection_failed(self, addr, exception):
+        self.answer(False)
+
+    def answer(self, result):
+        self.closed = True
+        try:
+            self.connection.close()
+        except AttributeError:
+            pass
+        self.resultfunc(result, self.downloadid, self.peerid, self.ip, self.port)
+
+    def read_header_len(self, s):
+        if ord(s) != len(protocol_name):
+            return None
+        return len(protocol_name), self.read_header
+
+    def read_header(self, s):
+        if s != protocol_name:
+            return None
+        return 8, self.read_reserved
+
+    def read_reserved(self, s):
+        return 20, self.read_download_id
+
+    def read_download_id(self, s):
+        if s != self.downloadid:
+            return None
+        return 20, self.read_peer_id
+
+    def read_peer_id(self, s):
+        if s != self.peerid:
+            return None
+        self.answer(True)
+        return None
+
+    def data_came_in(self, connection, s):
+        while True:
+            if self.closed:
+                return
+            i = self.next_len - self.buffer.tell()
+            if i > len(s):
+                self.buffer.write(s)
+                return
+            self.buffer.write(s[:i])
+            s = s[i:]
+            m = self.buffer.getvalue()
+            self.buffer.reset()
+            self.buffer.truncate()
+            x = self.next_func(m)
+            if x is None:
+                if not self.closed:
+                    self.answer(False)
+                return
+            self.next_len, self.next_func = x
+
+    def connection_lost(self, connection):
+        if not self.closed:
+            self.closed = True
+            self.resultfunc(False, self.downloadid, self.peerid, self.ip, self.port)
+
+    def connection_flushed(self, connection):
+        pass