# Acknowledging a call

SIP uses a three way handshake in placing a call. The called party answers the INVITE command by sending a 200 OK response, and this in turn is acknowledged by the calling side by sending an ACK. Normally the SIP stack automatically sends the ACK response; however, an application can override this behavior by setting the nmssip server configuration keyword generl.manualAck to true. Once done, the application can manually send an ACK by using nccAcknowledgeCall. This function is useful if the application sends an empty INVITE. In this case, the called side proposes the codec information in the 200 OK message and the response by the calling side is in the ACK response.

#### Prototype

DWORD NMSAPI nccAcknowledgeCall ( NCC_CALLHD callhd, void *acknowledgeparms)

Argument | Description
callhd | Call handle returned to the application with the NCCEVN_SEIZURE_DETECTED event or returned from nccPlaceCall.
acknowledgeparms | NULL or pointer to a buffer containing SIP IEs.

#### Example

ret = nccAcknowledgeCall( callhd, NULL );