diff --git a/Lib/asynchat.py b/Lib/asynchat.py
--- a/Lib/asynchat.py
+++ b/Lib/asynchat.py
@@ -56,8 +56,8 @@
 
     # these are overridable defaults
 
-    ac_in_buffer_size       = 4096
-    ac_out_buffer_size      = 4096
+    ac_in_buffer_size       = 65536
+    ac_out_buffer_size      = 65536
 
     # we don't want to enable the use of encoding by default, because that is a
     # sign of an application bug that we don't want to pass silently
diff --git a/Lib/asyncore.py b/Lib/asyncore.py
--- a/Lib/asyncore.py
+++ b/Lib/asyncore.py
@@ -532,7 +532,7 @@
 
     def initiate_send(self):
         num_sent = 0
-        num_sent = dispatcher.send(self, self.out_buffer[:512])
+        num_sent = dispatcher.send(self, self.out_buffer[:65536])
         self.out_buffer = self.out_buffer[num_sent:]
 
     def handle_write(self):