比如这样的* h5 u8 m8 F& y$ X7 B; w
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, a' n; \' w6 e+ ^OPTIONS sip:nm SIP/2.0
. ~0 o( z% p0 _' ?, bVia: SIP/2.0/TCP nm;branch=foo
4 U% E8 { W0 P% `% KFrom: <sip:nm@nm>;tag=root, B7 L" P2 u" g- D
To: <sip:nm2@nm2>* m4 _" H% S- q, H8 l/ g
Call-ID: 50000
3 E& `; R) P2 G+ l9 m% ~) e% J/ HCSeq: 42 OPTIONS2 X+ N( ~" H3 O* o; u5 G5 |! r
Max-Forwards: 70
6 Q7 n$ U, k2 Q( q1 j# i# P( g1 AContent-Length: 0
# u: ~9 [0 N% rContact: <sip:nm@nm>0 t; i8 N% ^, l
Accept: application/sdp
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