sipFactory = SipFactory.getInstance();
sipFactory.setPathName("gov.nist");
headerFactory = sipFactory.createHeaderFactory();
addressFactory = sipFactory.createAddressFactory();
messageFactory = sipFactory.createMessageFactory();
// If you get a request from a socket, you can use the jsip api to parse it.
String request = "INVITE sip:00001002000022@p25dr;user=TIA-P25-SU SIP/2.0\r\n"
+ "CSeq: 1 INVITE\r\n"
+ "From: <sip:0000100200000c@p25dr;user=TIA-P25-SU>;tag=841\r\n"
+ "To: <sip:00001002000022@p25dr;user=TIA-P25-SU>\r\n"