客户端请求流与sipsvr交互协议过程：
客户端--------invite with sdp--------》 sipsvr
客户端<-------invite 100 ok----------sipsvr
客户端<--------invite200ok with sdp---sipsvr
客户端-----------------ack--------------->sipsvr
抓包内容：
[root@localhost ~]# tcpdump -i ens32 host 192.168.12.51 and port 5060 -A tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on ens32, link-type EN10MB (Ethernet), capture size 65535 bytes 10:40:46.815176 IP 192.168.12.51.14762 > localhost.localdomain.sip: SIP, length: 549 E..AA...~.[P...3....9....-.IMESSAGE sip:11010000002000000001@192.168.15.225:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.12.51:14762;rport;branch=z9hG4bK263637728 From: <sip:11010000004000000001@11010000002000000001>;tag=3672408569 To: <sip:11010000002000000001@192.168.15.225:5060> Call-ID: 1971282934 CSeq: 20 MESSAGE Content-Type: Application/MANSCDP+xml Max-Forwards: 70 User-Agent: eXosip/4.0.0 Content-Length: 150 <?xml version="1.0"?> <Notify> <CmdType>Keepalive</CmdType> <SN>2</SN> <DeviceID>11010000004000000001</DeviceID> <Status>OK</Status> </Notify> 10:40:46.823084 IP localhost.localdomain.sip > 192.168.12.51.14762: SIP, length: 336 E..lM.@.@.N........3..9..X..SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.12.51:14762;rport;branch=z9hG4bK263637728 From: <sip:11010000004000000001@11010000002000000001>;tag=3672408569 To: <sip:11010000002000000001@192.168.15.225:5060>;tag=k83sIXXf Call-ID: 1971282934 CSeq: 20 MESSAGE Contact: <sip:11010000002000000001@192.168.15.225:5060> Content-Length: 0 10:40:51.834485 IP 192.168.12.51.14762 > localhost.localdomain.sip: SIP, length: 4 E.. A...~.]i...3....9....._.jaK............... 10:41:11.836074 IP 192.168.12.51.14762 > localhost.localdomain.sip: SIP, length: 4 E.. BW..~.]....3....9....._.jaK............... 10:41:21.903668 IP 192.168.12.51.14762 > localhost.localdomain.sip: SIP, length: 706 E...Bk..~.Z?...3....9.....>.INVITE sip:11010000002000000001@192.168.15.225:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.12.51:14762;rport;branch=z9hG4bK3392368037 From: <sip:11010000004000000001@1101000000>;tag=103530257 To: <sip:11010000001310000003@1101000000> Call-ID: 745314559 CSeq: 20 INVITE Contact: <sip:11010000004000000001@192.168.12.51:14762> Content-Type: application/sdp Max-Forwards: 70 User-Agent: eXosip/4.0.0 Subject: 11010000001310000003: 1, 11010000004000000001: Expires: 3600 Content-Length: 208 v=0 o=11010000004000000001 0 0 IN IP4 192.168.12.51 s=Play c=IN IP4 192.168.12.51 t=0 0 m=video 14764 RTP/AVP 96 98 97 a=recvonly a=rtpmap:96 PS/90000 a=rtpmap:98 H264/90000 a=rtpmap:97 MPEG4/90000 10:41:21.904681 IP localhost.localdomain.sip > 192.168.12.51.14762: SIP, length: 255 E...|.@.@..........3..9....}SIP/2.0 100 Trying Via: SIP/2.0/UDP 192.168.12.51:14762;rport=14762;branch=z9hG4bK3392368037 From: <sip:11010000004000000001@1101000000>;tag=103530257 To: <sip:11010000001310000003@1101000000> Call-ID: 745314559 CSeq: 20 INVITE Content-Length: 0 10:41:21.981467 IP localhost.localdomain.sip > 192.168.12.51.14762: SIP, length: 677 E...|.@.@..3.......3..9....#SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.12.51:14762;rport=14762;branch=z9hG4bK3392368037 Record-Route: <sip:11010000002000000001@192.168.15.225:5060;lr> From: <sip:11010000004000000001@1101000000>;tag=103530257 To: <sip:11010000001310000003@1101000000>;tag=q0ryOJUI Call-ID: 745314559 CSeq: 20 INVITE Contact: <sip:11010000001310000003@192.168.15.225:5060> Content-Type: application/sdp Content-Length: 256 v=0 o=11010000001310000003 0 0 IN IP4 192.168.12.93 s=Play c=IN IP4 192.168.12.93 t=0 0 m=video 36417 RTP/AVP 96 98 97 102 a=sendonly a=rtpmap:96 PS/90000 a=rtpmap:98 H264/90000 a=rtpmap:97 MPEG4/90000 a=rtpmap:102 HIKVISION/90000 y=0100000061 10:41:21.993081 IP 192.168.12.51.14762 > localhost.localdomain.sip: SIP, length: 456 E...Bm..~.[7...3....9.......ACK sip:11010000001310000003@192.168.15.225:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.12.51:14762;rport;branch=z9hG4bK2540914579 Route: <sip:11010000002000000001@192.168.15.225:5060;lr> From: <sip:11010000004000000001@1101000000>;tag=103530257 To: <sip:11010000001310000003@1101000000>;tag=q0ryOJUI Call-ID: 745314559 CSeq: 20 ACK Contact: <sip:11010000004000000001@192.168.12.51:14762> Max-Forwards: 70 User-Agent: eXosip/4.0.0 Content-Length: 0 10:41:26.546560 IP 192.168.12.51.14762 > localhost.localdomain.sip: SIP, length: 550 E..BB...~.Z....3....9.....E.MESSAGE sip:11010000002000000001@192.168.15.225:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.12.51:14762;rport;branch=z9hG4bK3352182078 From: <sip:11010000004000000001@11010000002000000001>;tag=1274993616 To: <sip:11010000002000000001@192.168.15.225:5060> Call-ID: 4200603033 CSeq: 20 MESSAGE Content-Type: Application/MANSCDP+xml Max-Forwards: 70 User-Agent: eXosip/4.0.0 Content-Length: 150 <?xml version="1.0"?> <Notify> <CmdType>Keepalive</CmdType> <SN>2</SN> <DeviceID>11010000004000000001</DeviceID> <Status>OK</Status> </Notify> 10:41:26.555111 IP localhost.localdomain.sip > 192.168.12.51.14762: SIP, length: 337 E..m.m@.@..........3..9..Y..SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.12.51:14762;rport;branch=z9hG4bK3352182078 From: <sip:11010000004000000001@11010000002000000001>;tag=1274993616 To: <sip:11010000002000000001@192.168.15.225:5060>;tag=mXHCNnEs Call-ID: 4200603033 CSeq: 20 MESSAGE Contact: <sip:11010000002000000001@192.168.15.225:5060> Content-Length: 0 ^C 10 packets captured 10 packets received by filter 0 packets dropped by kernel