Workaround #1134 by early checking if proxy closes connection

telethon/network/connection/tcpmtproxy.py

@@ -1,3 +1,4 @@
+import asyncio
 import hashlib
 import os
 
@@ -92,6 +93,28 @@ class TcpMTProxy(ObfuscatedConnection):
     packet_codec = None
     obfuscated_io = MTProxyIO
 
+    async def _connect(self, timeout=None, ssl=None):
+        await super()._connect(timeout=timeout, ssl=ssl)
+
+        # Wait for EOF for 2 seconds (or if _wait_for_data's definition
+        # is missing or different, just sleep for 2 seconds). This way
+        # we give the proxy a chance to close the connection if the current
+        # codec (which the proxy detects with the data we sent) cannot
+        # be used for this proxy. This is a work around for #1134.
+        # TODO Sleeping for N seconds may not be the best solution
+        # TODO This fix could be welcome for HTTP proxies as well
+        try:
+            await asyncio.wait_for(self._reader._wait_for_data('proxy'), 2)
+        except asyncio.TimeoutError:
+            pass
+        except Exception:
+            await asyncio.sleep(2)
+
+        if self._reader.at_eof():
+            self.disconnect()
+            raise ConnectionError(
+                'Proxy closed the connection after sending initial payload')
+
     @staticmethod
     def address_info(proxy_info):
         if proxy_info is None: