User guide

DC 900-1338I 157

Chapter

Client Applications —

Commands and Responses

This chapter presents the data structures required for the client application to exchange

messages with the ICP, followed by the details of the individual commands and

responses.

9.1 Client and ICP Interface Data Structures

The data link interface (DLI) provides a session-level interface between a client applica-

tion and the sample protocol software resident on an ICP. Messages traveling from the

client application go over the Ethernet to the Freeway server or ICP driver and end up

at the ICP. From the client’s perspective, these messages consist of data buffers supple-

mented with the DLI optional arguments data structure to provide the protocol-spe-

cific information required for Raw operation (refer back to Section 8.1.1.1 on

page 143). Figure9–1 shows the “C” definition of the DLI optional arguments struc-

ture.

From the ICP’s perspective, these messages consist of the

api_msg data structure shown

in Figure 9–2. The

icp_hdr structure is of type ICP_HDR and the prot_hdr structure is of

type

PROT_HDR, as shown in Figure 9–3.

Ta bl e 9 –1 shows the equivalent fields between the

DLI_OPT_ARGS structure and the

ICP_HDR and PROT_HDR structures. The client API translates between the

DLI_OPT_ARGS and the api_msg data structures. The usICPCommand field of the

DLI_OPT_ARGS structure corresponds to the command field of the ICP_HDR structure.

The

usProtCommand field of the DLI_OPT_ARGS structure corresponds to the command

field of the PROT_HDR structure.