fix empty content problem
fix empty content problem

ycaihua/tcpcopy,u20024804/tcpcopy,daodaoliang/tcpcopy,liviusATnetskope/second,horryq/tcpcopy,u20024804/tcpcopy,eliteYang/tcpcopy,ycaihua/tcpcopy,caosiyang/tcpcopy,sshling/tcpcopy,left2right/tcpcopy,left2right/tcpcopy,daodaoliang/tcpcopy,eliteYang/tcpcopy,liviusATnetskope/second,caosiyang/tcpcopy,wfxiang08/tcpcopy,sshling/tcpcopy,wfxiang08/tcpcopy,horryq/tcpcopy