Try Forwarding multiple messages per IO event notification.

examples/forward_poll.lua

@@ -11,14 +11,25 @@ xreq:bind('tcp://127.0.0.1:13333')
 local xrep = poll_zsock(c:socket(zmq.XREP))
 xrep:bind('tcp://127.0.0.1:13334')
 
+local max_recv = 10
+
 local function forward_io(src,dst)
 	src.on_data = function()
+		for i=1,max_recv do
 			repeat
-         local data = assert(src:recv(zmq.NOBLOCK))
+				local data, err = src:recv(zmq.NOBLOCK)
+					if not data then
+						if err == 'timeout' then
+							return
+						else
+							error("socket recv error:" .. err)
+						end
+					end
 				local more = src:getopt(zmq.RCVMORE) > 0
 				dst:send(data,more and zmq.SNDMORE or 0)
 			until not more
 		end
+	end
 end
 
 forward_io(xrep,xreq)