[Serusers] 400 bad request of SUBSCRIBE

hi I use pa module to support SUBSCRIBE request which Event header is "presence", and the function I used in ser.cfg is as follow : if (method=="SUBSCRIBE") {    if (!t_newtran()) {        log(1, "newtran error\n");        sl_reply_error();     };     handle_subscription("registrar");     break; }; But the response of  this request is 400 error while parsing header Server: SIP Express Route (0.9.6(i386/linux)) I find there is no place in source code to parse Server header I am I miss something in ser.cfg or any other modules should be loaded ? Could any one tell me why? ___________________________________________________________ 好玩贺卡等你发，邮箱贺卡全新上线！ http://card.mail.cn.yahoo.com/