问题 I have added a customized module named mod_confirm_delivery in ejabberd which has compiled and added successfully but when i am sending a message an error is coming in my ejabberd error log file, That is: 2016-03-15 17:03:38.306 [error] <0.2653.0>@ejabberd_hooks:run_fold1:368 {undef,[{mod_confirm_delivery,send_packet,[{xmlel,<<"iq">>,[{<<"xml:lang">>,<<"en">>},{<<"type">>,<<"get">>},{<<"id">>,<<"aacfa">>}],[{xmlcdata,<<"\n">>},{xmlel,<<"query">>,[{<<"xmlns">>,<<"jabber:iq:roster">>}],[]},