javax.sip.header
Interface ContactHeader

All Superinterfaces:

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

public interface ContactHeader

extends HeaderAddress, Parameters, Header

A Contact header field value provides a URI whose meaning depends on the type of request or response it is in. A Contact header field value can contain a display name, a URI with URI parameters, and header parameters.

The Contact header field provides a SIP or SIPS URI that can be used to contact that specific instance of the User Agent for subsequent requests. The Contact header field MUST be present and contain exactly one SIP or SIPS URI in any request that can result in the establishment of a dialog. For the methods defined in this specification, that includes only the INVITE request. For these requests, the scope of the Contact is global. That is, the Contact header field value contains the URI at which the User Agent would like to receive requests, and this URI MUST be valid even if used in subsequent requests outside of any dialogs.

If the Request-URI or top Route header field value contains a SIPS URI, the Contact header field MUST contain a SIPS URI as well.

Messages and Contact Headers

• Requests: A contact header is mandatory for INVITE's and optional for ACK, OPTIONS and REGISTER requests. This allows the callee to send future Requests, such as BYE Requests, directly to the caller instead of through a series of proxies.
• Informational Responses - A contact header is optional in a Informational Response to an INVITE request. It has the same semantics in an Informational Response as a Success Response.
• Success Responses - A contact header is mandatory in response to INVITE's and optional in response to OPTIONS and REGISTER requests. An user agent server sending a Success Response to an INIVTE must insert a ContactHeader in the Response indicating the SIP address under which it is reachable most directly for future SIP Requests.
• Redirection Responses - A contact header is optional in response to INVITE's, OPTIONS, REGISTER and BYE requests. A proxy may also delete the contact header.
• Ambiguous Header: - A contact header is optional in response to INVITE, OPTIONS, REGISTER and BYE requests.

The ContactHeader defines the Contact parameters "q" and "expires". The q-value value is used to prioritize addresses in a list of contact addresses. The expires value suggests an expiration interval that indicates how long the client would like a registration to be valid for a specific address. These parameters are only used when the Contact is present in a:

• REGISTER request
• REGISTER response
• 3xx response

For Example:
Contact: "Mr. Watson" sip:watson@worcester.jcp.org; q=0.7; expires=3600, "Mr. Watson" mailto:watson@jcp.org.com; q=0.1

See Also:

HeaderAddress, Parameters

Field Summary

static java.lang.String

NAME Name of ContactHeader

Method Summary

int	getExpires() Returns the value of the expires parameter.
float	getQValue() Returns the value of the q-value parameter of this ContactHeader.
void	setExpires(int expires) Returns the value of the expires parameter as delta-seconds.
void	setQValue(float qValue) Sets the qValue value of the Name Address.

Methods inherited from interface javax.sip.header.HeaderAddress

getAddress, setAddress

Methods inherited from interface javax.sip.header.Parameters

getParameter, getParameterNames, removeParameter, setParameter

Methods inherited from interface javax.sip.header.Header

clone, equals, getName, toString

Field Detail

NAME

public static final java.lang.String NAME

Name of ContactHeader

See Also:

Constant Field Values

Method Detail

setExpires

public void setExpires(int expires)
                throws InvalidArgumentException

Returns the value of the expires parameter as delta-seconds. When a client sends a REGISTER request, it MAY suggest an expiration interval that indicates how long the client would like the registration to be valid for a specific address. There are two ways in which a client can suggest an expiration interval for a binding:

• through an Expires header field
• an "expires" Contact header parameter.

The latter allows expiration intervals to be suggested on a per-binding basis when more than one binding is given in a single REGISTER request, whereas the former suggests an expiration interval for all Contact header field values that do not contain the "expires" parameter. If neither mechanism for expressing a suggested expiration time is present in a REGISTER, the client is indicating its desire for the server to choose.

A User Agent requests the immediate removal of a binding by specifying an expiration interval of "0" for that contact address in a REGISTER request. User Agents SHOULD support this mechanism so that bindings can be removed before their expiration interval has passed. The REGISTER-specific Contact header field value of "*" applies to all registrations, but it MUST NOT be used unless the Expires header field is present with a value of "0". The "*" value can be determined if "this.getNameAddress().isWildcard() = = true".

Throws:

InvalidArgumentException - if supplied value is less than zero.

Since:

v1.1

getExpires

public int getExpires()

Returns the value of the expires parameter.

Returns:

value of the expires parameter measured in delta-seconds, O implies removal of Registration specified in Contact Header.

Since:

v1.1

setQValue

public void setQValue(float qValue)
               throws InvalidArgumentException

Sets the qValue value of the Name Address. If more than one Contact is sent in a REGISTER request, the registering UA intends to associate all of the URIs in these Contact header field values with the address-of-record present in the To field. This list can be prioritized with the "q" parameter in the Contact header field. The "q" parameter indicates a relative preference for the particular Contact header field value compared to other bindings for this address-of-record. A value of -1 indicates the qValue paramater is not set.

Parameters:

qValue - - the new float value of the q-value parameter.

Throws:

InvalidArgumentException - if the q-value parameter value is not -1 or between 0 and 1.

Since:

v1.1

getQValue

public float getQValue()

Returns the value of the q-value parameter of this ContactHeader. The q-value parameter indicates the relative preference amongst a set of locations. q-values are decimal numbers from 0 to 1, with higher values indicating higher preference.

Returns:

the q-value parameter of this ContactHeader, -1 if the q-value is not set.

Since:

v1.1