a note about sbcl and slime

recently I switch to stumpwm,getting it work with sbcl,I enjoyed hacking.
but then I found that when slime read or print Chinese characters,the connection to sbcl will be broken.
Actually,I did set slime-net-coding-system to utf-8-unix,which dosen't help at all.
At last the problem turned out to be due to the coding system of swank side.
as we know,slime connects to a server that was provided by a package named swank.
if I type M-x slime in emacs,everything works well cause emacs runs an sbcl process and set coding system at both side for me,but when sbcl started seperatly by xdm from slime,I forgot to set coding system of swank.
so after I start swank like this:

(swank:create-server :dont-close t :coding-system "uft-8-unix")

I can input Chinese and get correct output at REPL.