fix rtt for realtime copying
fix rtt for realtime copying

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