req.setRequestLine(new RequestLine(method,request_uri));
ViaHeader via=new ViaHeader(proto,via_addr,host_port);
if (rport) via.setRport();
if (branch==null) branch=SipProvider.pickBranch();
via.setBranch(branch);
req.addViaHeader(via);
req.setMaxForwardsHeader(new MaxForwardsHeader(70));
if (remote_tag==null) req.setToHeader(new ToHeader(to));
else req.setToHeader(new ToHeader(to,remote_tag));
req.setFromHeader(new FromHeader(from,local_tag));
req.setCallIdHeader(new CallIdHeader(call_id));