[Home](./index.md) > [sip.js](./sip.js.md) > [UserAgentClient](./sip.js.useragentclient.md) ## UserAgentClient class User Agent Client (UAC). Signature: ```typescript export declare class UserAgentClient implements OutgoingRequest ``` ## Remarks A user agent client is a logical entity that creates a new request, and then uses the client transaction state machinery to send it. The role of UAC lasts only for the duration of that transaction. In other words, if a piece of software initiates a request, it acts as a UAC for the duration of that transaction. If it receives a request later, it assumes the role of a user agent server for the processing of that transaction. https://tools.ietf.org/html/rfc3261\#section-6 ## Constructors | Constructor | Modifiers | Description | | --- | --- | --- | | [(constructor)(transactionConstructor, core, message, delegate)](./sip.js.useragentclient._constructor_.md) | | Constructs a new instance of the UserAgentClient class | ## Properties | Property | Modifiers | Type | Description | | --- | --- | --- | --- | | [core](./sip.js.useragentclient.core.md) | | UserAgentCore | | | [delegate](./sip.js.useragentclient.delegate.md) | | OutgoingRequestDelegate | undefined | | | [logger](./sip.js.useragentclient.logger.md) | | Logger | | | [loggerFactory](./sip.js.useragentclient.loggerfactory.md) | | LoggerFactory | | | [message](./sip.js.useragentclient.message.md) | | OutgoingRequestMessage | | | [transaction](./sip.js.useragentclient.transaction.md) | | ClientTransaction | The transaction associated with this request. | ## Methods | Method | Modifiers | Description | | --- | --- | --- | | [authenticationGuard(message)](./sip.js.useragentclient.authenticationguard.md) | | If a 401 (Unauthorized) or 407 (Proxy Authentication Required) response is received, the UAC SHOULD follow the authorization procedures of Section 22.2 and Section 22.3 to retry the request with credentials. https://tools.ietf.org/html/rfc3261\#section-8.1.3.5 22 Usage of HTTP Authentication https://tools.ietf.org/html/rfc3261\#section-22 22.1 Framework https://tools.ietf.org/html/rfc3261\#section-22.1 22.2 User-to-User Authentication https://tools.ietf.org/html/rfc3261\#section-22.2 22.3 Proxy-to-User Authentication https://tools.ietf.org/html/rfc3261\#section-22.3FIXME: This "guard for and retry the request with credentials" implementation is not complete and at best minimally passable. | | [cancel(reason, options)](./sip.js.useragentclient.cancel.md) | | Since requests other than INVITE are responded to immediately, sending a CANCEL for a non-INVITE request would always create a race condition. A CANCEL request SHOULD NOT be sent to cancel a request other than INVITE. https://tools.ietf.org/html/rfc3261\#section-9.1 | | [dispose()](./sip.js.useragentclient.dispose.md) | | | | [onRequestTimeout()](./sip.js.useragentclient.onrequesttimeout.md) | | 8.1.3.1 Transaction Layer Errors In some cases, the response returned by the transaction layer will not be a SIP message, but rather a transaction layer error. When a timeout error is received from the transaction layer, it MUST be treated as if a 408 (Request Timeout) status code has been received. If a fatal transport error is reported by the transport layer (generally, due to fatal ICMP errors in UDP or connection failures in TCP), the condition MUST be treated as a 503 (Service Unavailable) status code. https://tools.ietf.org/html/rfc3261\#section-8.1.3.1 | | [onTransportError(error)](./sip.js.useragentclient.ontransporterror.md) | | 8.1.3.1 Transaction Layer Errors In some cases, the response returned by the transaction layer will not be a SIP message, but rather a transaction layer error. When a timeout error is received from the transaction layer, it MUST be treated as if a 408 (Request Timeout) status code has been received. If a fatal transport error is reported by the transport layer (generally, due to fatal ICMP errors in UDP or connection failures in TCP), the condition MUST be treated as a 503 (Service Unavailable) status code. https://tools.ietf.org/html/rfc3261\#section-8.1.3.1 | | [receiveResponse(message)](./sip.js.useragentclient.receiveresponse.md) | | Receive a response from the transaction layer. |