diff --git a/Doc/library/asyncore.rst b/Doc/library/asyncore.rst
--- a/Doc/library/asyncore.rst
+++ b/Doc/library/asyncore.rst
@@ -209,7 +209,11 @@
 
       Read at most *buffer_size* bytes from the socket's remote end-point.  An
       empty string implies that the channel has been closed from the other end.
+      None can be returned in case the socket was not ready to be read in which
+      case the application should just 'pass'.
 
+      .. versionchanged:: 3.4
+         None can be returned
 
    .. method:: listen(backlog)
 
diff --git a/Lib/asynchat.py b/Lib/asynchat.py
--- a/Lib/asynchat.py
+++ b/Lib/asynchat.py
@@ -118,6 +118,8 @@
             self.handle_error()
             return
 
+        if data is None:
+            return
         if isinstance(data, str) and self.use_encoding:
             data = bytes(str, self.encoding)
         self.ac_in_buffer = self.ac_in_buffer + data
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 None
             else:
                 raise