diff --git a/Lib/asynchat.py b/Lib/asynchat.py
--- a/Lib/asynchat.py
+++ b/Lib/asynchat.py
@@ -132,6 +132,8 @@
 
         if isinstance(data, str) and self.use_encoding:
             data = bytes(str, self.encoding)
+        if data == '':
+            return
         self.ac_in_buffer = self.ac_in_buffer + data
 
         # Continue to search for self.terminator in self.ac_in_buffer,
diff --git a/Lib/asyncore.py b/Lib/asyncore.py
--- a/Lib/asyncore.py
+++ b/Lib/asyncore.py
@@ -59,6 +59,8 @@
 
 _DISCONNECTED = frozenset((ECONNRESET, ENOTCONN, ESHUTDOWN, ECONNABORTED, EPIPE,
                            EBADF))
+_RETRY = frozenset((EWOULDBLOCK, EAGAIN))
+
 
 try:
     socket_map
@@ -389,6 +391,8 @@
             if why.args[0] in _DISCONNECTED:
                 self.handle_close()
                 return b''
+            elif why.args[0] in _RETRY:
+                return b''
             else:
                 raise