[SIP]Message

@Override
    protected void doMessage(SipServletRequest req) throws ServletException, IOException{
        SipApplicationSession sas = this.getSas(req.getFrom());//取得用户A的SipApplicationSession
        if(sas != null){
            Proxy proxy = req.getProxy();//取得Proxy
            proxy.setRecordRoute(true);
            proxy.setSupervised(true);
            SipUser sipuser = this.getSipuser(req.getTo());
            if (sipuser != null){
                proxy.proxyTo(sipuser.getContact());//将请求代理给B
            }
        }
    }

SipUser su = null;
        su = this.getSipuser(req.getTo();//取得用户B
        if(su == null){
            req.createResponse(SipServletResponse.SC_NOT_FOUND).send();//如果不存在,返回404给A
        } else {
            req.createResponse(SipServletResponse.SC_OK).send();//如果存在返回200OK给A
//创建新的请求
            SipServletRequest newReq = sf.createRequest(sf.createApplicationSession(), req.getMethod(), Sipfrom, Sipto);
            //set Message设置请求
            Object content = null;
            content = req.getContent();
            String contentType = "";
            contentType = req.getContentType();
            if(content != null && !(contentType.equals("")))
                newReq.setContent(content, contentType);
            URI contact = sf.createURI(su.getContact().toString());
            newReq.setRequestURI(contact); //设置请求的URI
            newReq.send();//发送请求给B
        }
        if(req.getApplicationSession() != null)
            req.getApplicationSession().invalidate();//使A的SipApplicationSession失效,可以减少内存