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9.3.2.4 C-FIND Protocol Procedures
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#### 9.3.2.4 C-FIND Protocol Procedures

The C-FIND procedures are initiated by the invoking DIMSE-service-user issuing a C-FIND request primitive. On receipt of the C-FIND request primitive the DIMSE-C protocol machine shall:

- construct a Message conveying the C-FIND-RQ

- send the Message using the P-DATA request service (see 8.1)

On receipt of a Message conveying a C-FIND-RQ the DIMSE-C protocol machine shall issue a C-FIND indication primitive to the performing DIMSE-service-user.

The DIMSE-C protocol machine shall:

- accept zero or more C-FIND response primitives containing the status of Pending, issued by the performing DIMSE-service-user, followed by a single C-FIND response primitive containing the final status

- for each C-FIND response primitive containing the Pending status the DIMSE-C protocol machine shall:

  1. construct a Message conveying the (Pending) C-FIND-RSP

  2. send the Message using the P-DATA request service (see 8.1)

- for the C-FIND response primitive containing the final status the DIMSE-C protocol machine shall:

  1. construct a Message conveying the (final) C-FIND-RSP

  2. end the Message using the P-DATA request service (see 8.1)

On receipt of a Message conveying a C-FIND-RSP the DIMSE-C protocol machine shall:

- if the Message indicates the status of Pending, issue a C-FIND confirmation primitive to the invoking DIMSE-service-user with a Pending status

- if the Message indicates a final status, issue a C-FIND confirmation primitive to the invoking DIMSE-service-user with a final status, thus completing the C-FIND procedure

### Note

The C-FIND procedures can be canceled at any time by the invoking DIMSE-service-user. This is accomplished by the invoking DIMSE-service-user issuing a C-CANCEL request primitive.

The performing DIMSE-service-user may return a C-FIND-RSP with the status of Failed or Refused before the complete C-FIND-RQ request Message has been completely transmitted by the invoking DIMSE-service-user (this is called an early failed response). Upon receipt of this Failed or Refused C-FIND-RSP the invoking DIMSE-service-user may terminate the Message before it is completely sent (i.e., set the Last Fragment bit to 1 in a Data PDV for this Message, see Annex F). Following this, it may invoke another operation or notification. It is a protocol violation for an invoking DIMSE-service-user to set the Last Fragment bit to 1 before a C-FIND-RQ Message has been completely transmitted if it has not received a Failed or Refused C-FIND-RSP to that request.

### Note

When an Association is operating in asynchronous mode, it is possible for an invoking DIMSE-service-user to transmit several Messages before a response. Therefore, while sending a Message it may receive a response to a previously transmitted Message. In this case this response is not an early failed response because the related Message has already been sent.

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DICOM PS3.7 2018a - Message Exchange