jain.protocol.ip.sip.header
Class CSeqHeader

java.lang.Object
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  +--jain.protocol.ip.sip.header.Header
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        +--jain.protocol.ip.sip.header.GeneralHeader
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              +--jain.protocol.ip.sip.header.CSeqHeader

public final class CSeqHeader

extends GeneralHeader

This class represents the CSeq (command sequence) general-header. Clients must add the CSeqHeader to every RequestMessage. A CSeqHeader in a RequestMessage contains the RequestMessage method and a single decimal sequence number chosen by the requesting client, unique within a single value of Call-ID. The sequence number must be expressible as a 32-bit unsigned integer. The initial value of the sequence number is arbitrary, but must be less than 2**31. Consecutive RequestMessages that differ in method, headers or body, but have the same CallIDHeader must contain strictly monotonically increasing and contiguous sequence numbers; sequence numbers do not wrap around. Retransmissions of the same request carry the same equence number, but an InviteMessage with a different message body or different headers (a "re-invitation") acquires a new, higher sequence number. A server must echo the CSeqHeader from the RwquestMessage in its ResponseMessage. If the Method value is missing in the received CSeqHeader, the server fills it in appropriately.

AckMessages and CancelMessages must contain the same CSeqHeader sequence number (but not method) as the InviteMessages they refer to, while a ByeMessage cancelling an invitation must have a higher sequence number. A ByeMessage with a CSeqHeader sequence number that is not higher should cause a BAD_REQUEST ResponseMessage to be generated.

A user agent server must remember the highest sequence number for any InviteMessage with the same CallIdHeader. The server must respond to, and then discard, any InviteMessage with a lower sequence number.

All RequestMessages spawned in a parallel search have the same CSeqHeader as the RequestMessage triggering the parallel search.

The Method value allows the client to distinguish the response to an InviteMessage from that of a response to a CancelMessage. CancelMessages can be generated by proxies; if they were to increase the sequence number, it might conflict with a later RequestMessage issued by the user agent for the same call.

Forked RequestMessages must have the same CSeqHeader as there would be ambiguity otherwise between these forked RequestMessages and later ByeMessages issued by the client user agent.

Version:

0.6

Field Summary

static java.lang.String

token Token of CSeqHeader

Fields inherited from class jain.protocol.ip.sip.header.Header

ENTITY_HEADER, GENERAL_HEADER, REQUEST_HEADER, RESPONSE_HEADER

Constructor Summary

CSeqHeader(int sequenceNumber, java.lang.String method)
Creates a CSeqHeader based on given sequence number and method

Method Summary

java.lang.Object	clone() Creates and returns a copy of CSeqHeader
boolean	equals(CSeqHeader cSeqHeader) Indicates whether some other CSeqHeader is "equal to" this one
java.lang.String	getMethod() Gets method of CSeqHeader
int	getSequenceNumber() Gets sequence number of CSeqHeader
java.lang.String	getValue() Gets value of CSeqHeader
void	setMethod(java.lang.String method) Set method of CSeqHeader
void	setSequenceNumber(int sequenceNumber) Set sequence number of CSeqHeader

Methods inherited from class jain.protocol.ip.sip.header.Header

equals, getHeaderType, getToken, setValue, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

token

public static final java.lang.String token

Token of CSeqHeader

Constructor Detail

CSeqHeader

public CSeqHeader(int sequenceNumber,
                  java.lang.String method)
           throws java.lang.IllegalArgumentException

Creates a CSeqHeader based on given sequence number and method

Parameters:

sequenceNumber - sequence number

method - method

Throws:

java.lang.IllegalArgumentException - if sequenceNumber is negative, or if method is null or zero-length

Method Detail

setSequenceNumber

public void setSequenceNumber(int sequenceNumber)
                       throws java.lang.IllegalArgumentException

Set sequence number of CSeqHeader

Parameters:

sequenceNumber - sequence number

Throws:

java.lang.IllegalArgumentException - if sequenceNumber is negative

setMethod

public void setMethod(java.lang.String method)
               throws java.lang.IllegalArgumentException

Set method of CSeqHeader

Parameters:

method - method

Throws:

java.lang.IllegalArgumentException - if method is null or zero-length

getSequenceNumber

public int getSequenceNumber()

Gets sequence number of CSeqHeader

Returns:

sequence number of CSeqHeader

getMethod

public java.lang.String getMethod()

Gets method of CSeqHeader

Returns:

method of CSeqHeader

getValue

public java.lang.String getValue()

Gets value of CSeqHeader

Overrides:

getValue in class Header

Returns:

value of CSeqHeader

clone

public java.lang.Object clone()

Creates and returns a copy of CSeqHeader

Overrides:

clone in class Header

equals

public boolean equals(CSeqHeader cSeqHeader)

Indicates whether some other CSeqHeader is "equal to" this one

Parameters:

cSeqHeader - the CSeqHeader with which to compare