D.4 Networking
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## D.4 Networking

### D.4.1 Implementation Model

#### D.4.1.1 Application Data Flow

Figure D.4.1-1. Implementation Model

The application is a single pure Java application that provides both a user interface, internal database and network listener that spawns additional threads as necessary to handle incoming connections, as well as media support.

Conceptually the network services may be modeled as the following separate AEs, though in fact all the AEs share a single (configurable) AE Title:

- ECHO-SCP, which responds to verification requests

- STORAGE-SCP, which receives incoming images and other composite instances

- STORAGE-SCU, which sends outbound images and other composite instances

- FIND-SCU, which queries remote AEs for lists of studies, series and instances

- MOVE-SCU, which retrieves selected studies, series or instances

#### D.4.1.2 Functional Definitions of AEs

##### D.4.1.2.1 ECHO-SCP

ECHO-SCP waits in the background for connections, will accept associations with Presentation Contexts for SOP Class of the Verification Service Class, and will respond successfully to echo requests.

##### D.4.1.2.2 STORAGE-SCP

STORAGE-SCP waits in the background for connections, will accept associations with Presentation Contexts for SOP Classes of the Storage Service Class, and will store the received instances to the local database where they may subsequently be listed and viewed through the user interface.

##### D.4.1.2.3 STORAGE-SCU

STORAGE-SCU is activated through the user interface when a user selects instances from the local database or a DICOMDIR, or the currently displayed instance, and requests that they be sent to a remote AE (selected from a pre-configured list).

##### D.4.1.2.4 FIND-SCU

FIND-SCU is activated through the user interface when a user selects a remote AE to query (from a pre-configured list), then initiates a query. Queries are performed recursively from the study through the series and instance levels until all matching instances have been listed.

##### D.4.1.2.5 MOVE-SCU

MOVE-SCU is activated through the user interface when a user selects a study, series or instance for retrieval. A connection to the remote AE is established to initiate and monitor the retrieval and the STORAGE-SCP AE receives the retrieved instances.

#### D.4.1.3 Sequencing of Real-World Activities

All SCP activities are performed asynchronously in the background and not dependent on any sequencing.

All SCU activities are sequentially initiated in the user interface, and another activity may not be initiated until the prior activity has completed.

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