Echelon OpenLDV User Manual download pdf (Page 44)

36 Using the OpenLDV API

information. If you do not specify a valid network interface name as the id

parameter when you call this function, or if the network interface referenced by

the id parameter cannot be found, the LDV_INVALID_DEVICE_ID or

LDVX_INVALID_XDRIVER return code is returned.

Each network interface can only be part of one OpenLDV session at a time on a

particular computer. If you call this function for a network interface that is being

used by another process on your computer, the function will fail, and the

LDV_ACCESS_DENIED return code is returned.

If you use xDriver to open a remote network interface while a remote client on

another computer is using it, the call to ldvx_open() might initially appear to

succeed. However, when you call ldv_read() or ldv_write() to read or write a

message to the network interface later, the LDVX_READ_FAILED or

LDVX_WRITE_FAILED failure code is returned, indicating that the session has

failed. The timing of the failure depends on the setting of the Synchronous

Timeout field of the xDriver profile that is handling the session, as well as the

setting of the TcpMaxConnectRetransmissions parameter on the computer

that is running the application. For more information about xDriver profiles, see

xDriver Profiles on page 134.

ldvx_register_window()

Call this function to register a Windows HWND object for receiving session

change notifications.

Syntax

LDVCode ldvx_register_window(

LdvHandle handle,

HWND hWnd,

LONG tag

)

Table 21. ldvx_register_window() Parameters

Parameter Direction Description

handle

Input The session handle for the network interface. This value

was returned as the handle parameter when you opened the

network interface with one of the open functions

(ldv_open(), ldv_open_cap(), or ldvx_open()).

hWnd Input The Windows handle for the session state change or

attachment notification messages, where available (for

example, from an xDriver device or a USB network

interface). This handle replaces any previously set handle

(such as one from one of the open functions).

If NULL, OpenLDV stops sending notifications.

See Windows Messages for Session Notifications on page 44.

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Echelon OpenLDV User Manual Page 44