[SIPForum-discussion] What is the port number in "Invite" request-line? Thanks

[Yuantao Zhang]

Dear all

 

INVITE sip:bob at biloxi.com SIP/2.0:5555

INVITE sip:bob at biloxi.com SIP/2.0

 

Above are 2 "Invite" request-line examples. In example one, it indicates
a port number, 5555. What does the port number mean? 

 

Is it the port number of SIP proxy? Why we include port number here? The
SIP proxy(biloxi.com) application layer who receives this "Invite"
should receive this via port 5555 from lowe layer(UDP). Therefore, The
SIP proxy(biloxi.com) application layer already know the port is 5555.
Actualy, the SIP proxy application layer keeps listening port 5555. 

 

The second "Invite" request-line example is from RFC3261 and does not
include port number. Can I say the port number is useless? So why
example one includes a useless part in "Invite" request-line URL? 

 

Or is the port number is which the UAS is listening to? How the UAC
knows it is 5555 if so? 

 

Any standard on this port number issue? Thanks. 

 

Best regards

Steven

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