javax.sip.header

Interface CSeqHeader

All Superinterfaces:

Cloneable, Header, Serializable

All Known Implementing Classes:

CSeq

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

Version:

1.2

Author:

BEA Systems, NIST

Field Summary

Fields

Modifier and Type	Field and Description
static String	NAME Name of the CSeqHeader

Method Summary

Methods

Modifier and Type	Method and Description
boolean	equals(Object obj) Compare this CSeqHeader for equality with another.
String	getMethod() Gets the method of CSeqHeader
long	getSeqNumber() Gets the sequence number of this CSeqHeader.
int	getSequenceNumber() Deprecated. This method is replaced with getSeqNumber() with type long.
void	setMethod(String method) Sets the method of CSeqHeader
void	setSeqNumber(long sequenceNumber) Sets the sequence number value of the CSeqHeader.
void	setSequenceNumber(int sequenceNumber) Deprecated. This method is replaced with setSeqNumber(long) with type long.

Methods inherited from interface javax.sip.header.Header

clone, getName, hashCode, toString

Field Detail

NAME

static final String NAME

Name of the CSeqHeader

See Also:

Constant Field Values

Method Detail

setMethod

void setMethod(String method)
               throws ParseException

Sets the method of CSeqHeader

Parameters:

method - - the method of the Request of this CSeqHeader

Throws:

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

getMethod

String getMethod()

Gets the method of CSeqHeader

Returns:

method of CSeqHeader

setSequenceNumber

void setSequenceNumber(int sequenceNumber)
                       throws InvalidArgumentException

Deprecated. This method is replaced with setSeqNumber(long) with type long.

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**32 -1

Parameters:

sequenceNumber - - the new sequence number of this CSeqHeader

Throws:

InvalidArgumentException - if supplied value is less than zero.

Since:

v1.1

getSequenceNumber

int getSequenceNumber()

Deprecated. This method is replaced with getSeqNumber() with type long.

Gets the sequence number of this CSeqHeader.

Returns:

sequence number of the CSeqHeader

Since:

v1.1

setSeqNumber

void setSeqNumber(long sequenceNumber)
                  throws InvalidArgumentException

Sets the sequence number value of the CSeqHeader.

Parameters:

sequenceNumber - - the new sequence number of this CSeqHeader

Throws:

InvalidArgumentException - if supplied value is less than zero.

Since:

v1.2

getSeqNumber

long getSeqNumber()

Gets the sequence number of this CSeqHeader.

Returns:

sequence number of the CSeqHeader

Since:

v1.2

equals

boolean equals(Object obj)

Compare this CSeqHeader for equality with another. This method overrides the equals method in javax.sip.Header. This method specifies object equality as outlined by RFC3261. Two CSeq header fields are considered equal if the sequence number and the request method are identical. When comparing header fields, field names are always case-insensitive. Unless otherwise stated in the definition of a particular header field, field values, parameter names, and parameter values are case-insensitive. Tokens are always case-insensitive. Unless specified otherwise, values expressed as quoted strings are case-sensitive.

Specified by:

equals in interface Header

Overrides:

equals in class Object

Parameters:

obj - the object to compare this CSeqHeader with.

Returns:

true if obj is an instance of this class representing the same CseqHeader as this, false otherwise.

Since:

v1.2