diff --git a/Lib/asyncore.py b/Lib/asyncore.py
--- a/Lib/asyncore.py
+++ b/Lib/asyncore.py
@@ -526,13 +526,16 @@
 
 class dispatcher_with_send(dispatcher):
 
+    # send() buffer size
+    BUFSIZE = 8192
+
     def __init__(self, sock=None, map=None):
         dispatcher.__init__(self, sock, map)
         self.out_buffer = b''
 
     def initiate_send(self):
         num_sent = 0
-        num_sent = dispatcher.send(self, self.out_buffer[:512])
+        num_sent = dispatcher.send(self, self.out_buffer[:self.BUFSIZE])
         self.out_buffer = self.out_buffer[num_sent:]
 
     def handle_write(self):