call skynet.trace() in example

examples/agent.lua

@@ -50,7 +50,10 @@ skynet.register_protocol {
 	unpack = function (msg, sz)
 		return host:dispatch(msg, sz)
 	end,
-	dispatch = function (_, _, type, ...)
+	dispatch = function (fd, _, type, ...)
+		assert(fd == client_fd)	-- You can use fd to reply message
+		skynet.ignoreret()	-- session is fd, don't call skynet.ret
+		skynet.trace()
 		if type == "REQUEST" then
 			local ok, result  = pcall(request, ...)
 			if ok then
@@ -92,6 +95,7 @@ end
 
 skynet.start(function()
 	skynet.dispatch("lua", function(_,_, command, ...)
+		skynet.trace()
 		local f = CMD[command]
 		skynet.ret(skynet.pack(f(...)))
 	end)