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##

# TCPIP_DNS_HandlerRegister Function

## C

    TCPIP_DNS_HANDLE TCPIP_DNS_HandlerRegister(
        TCPIP_NET_HANDLE hNet,
        TCPIP_DNS_EVENT_HANDLER handler,
        const void* hParam
    );

## Description

This function registers a DNS client event handler. The DNS client module will call the registered handler when a DNS client event (TCPIP_DNS_EVENT_TYPE) occurs.

## Preconditions

The DNS module must be initialized.

## Paramaters

Parameters | Description
--- | ---
hNet | Interface handle. Use hNet == 0 to register on all interfaces available.
handler | Handler to be called when a DNS client event occurs.
hParam | Pointer to non-volatile ASCIIZ string to be used in the handler call. It is used as a domain/host name. If not NULL, a DNS notification will be delivered only for a name resolution that matches the hParam. If the hParam == 0, then the notification is triggered for any host name resolution.

## Returns

- Returns a valid handle if the call succeeds.
- Returns null handle if the call failed (out of memory, for example).

## Remarks

The handler has to be short and fast. It is meant for setting an event flag, not for lengthy processing.