--- a/net/server_epoll.lua	Wed May 02 19:06:59 2018 +0200
+++ b/net/server_epoll.lua	Wed May 02 19:20:29 2018 +0200
@@ -336,6 +336,7 @@
 -- Called when socket is writable
 function interface:onwritable()
 	self:onconnect();
+	if not self.conn then return; end -- could have been closed in onconnect
 	local buffer = self.writebuffer;
 	local data = t_concat(buffer);
 	local ok, err, partial = self.conn:send(data);