javax.sip.header
Interface CSeqHeader

All Superinterfaces:

java.lang.Cloneable, Header, java.io.Serializable

public interface CSeqHeader

extends Header

A CSeq header field in a request contains a single decimal sequence number and the request method. The CSeq header field serves to identify and order transactions within a dialog, to provide a means to uniquely identify transactions, and to differentiate between new requests and request retransmissions. Two CSeq header fields are considered equal if the sequence number and the request method are identical.

• Method - The method part of CSeq is case-sensitive and MUST match that of the request.
• Sequence number - The sequence number is chosen by the requesting client and is unique within a single value of Call-ID. The sequence number MUST be expressible as a 32-bit unsigned integer and MUST be less than 2**31. For non-REGISTER requests outside of a dialog, the sequence number value is arbitrary. Consecutive Requests 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 sequence number, but an INVITE Request 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 Request in its Response. If the method value is missing in the received CSeqHeader, the server fills it in appropriately. ACK and CANCEL Requests must contain the same CSeqHeader sequence number (but not method) as the INVITE Request they refer to, while a BYE Request cancelling an invitation must have a higher sequence number. An user agent server must remember the highest sequence number for any INVITE Request with the same CallIdHeader. The server must respond to, and then discard, any INVITE Request with a lower sequence number.

As long as a client follows the above guidelines, it may use any mechanism it would like to select CSeq header field values.

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

For Example:
CSeq: 4711 INVITE

Field Summary

static java.lang.String

NAME Name of the CSeqHeader

Method Summary

java.lang.String	getMethod() Gets the method of CSeqHeader
int	getSequenceNumber() Gets the sequence number of this CSeqHeader.
void	setMethod(java.lang.String method) Sets the method of CSeqHeader
void	setSequenceNumber(int sequenceNumber) Sets the sequence number value of the CSeqHeader.

Methods inherited from interface javax.sip.header.Header

clone, equals, getName, toString

Field Detail

NAME

public static final java.lang.String NAME

Name of the CSeqHeader

See Also:

Constant Field Values

Method Detail

setMethod

public void setMethod(java.lang.String method)
               throws java.text.ParseException

Sets the method of CSeqHeader

Parameters:

method - - the method of the Request of this CSeqHeader

Throws:

java.text.ParseException - which signals that an error has been reached unexpectedly while parsing the method value.

getMethod

public java.lang.String getMethod()

Gets the method of CSeqHeader

Returns:

method of CSeqHeader

setSequenceNumber

public void setSequenceNumber(int sequenceNumber)
                       throws InvalidArgumentException

Sets the sequence number value of the CSeqHeader. The sequence number MUST be expressible as a 32-bit unsigned integer and MUST be less than 2**31.

Parameters:

sequenceNumber - - the new sequence number of this CSeqHeader

Throws:

InvalidArgumentException - if supplied value is less than zero.

Since:

v1.1

getSequenceNumber

public int getSequenceNumber()

Gets the sequence number of this CSeqHeader.

Returns:

sequence number of the CSeqHeader

Since:

v1.1