lineAccept function (tapi.h)

The lineAccept function accepts the specified offered call. It can optionally send the specified user-user information to the calling party.


LONG lineAccept(
  HCALL  hCall,
  LPCSTR lpsUserUserInfo,
  DWORD  dwSize



Handle to the call to be accepted. The application must be an owner of the call. Call state of hCall must be offering.


Pointer to a null-terminated string containing user-user information to be sent to the remote party as part of the call accept. This pointer can be left NULL if no user-user information is to be sent. User-user information is only sent if supported by the underlying network (see LINEDEVCAPS). The protocol discriminator member for the user-user information, if required, should appear as the first byte of the buffer pointed to by lpsUserUserInfo, and must be accounted for in dwSize.


Size of the user-user information in lpsUserUserInfo (including the null terminator), in bytes. If lpsUserUserInfo is NULL, no user-user information is sent to the calling party and dwSize is ignored.

Return value

Returns a positive request identifier if the function is completed asynchronously, or a negative error number if an error occurs. The dwParam2 parameter of the corresponding LINE_REPLY message is zero if the function succeeds, or it is a negative error number if an error occurs. Possible return values are:



The lineAccept function is used in telephony environments like Integrated Services Digital Network (ISDN) that allow alerting associated with incoming calls to be separate from the initial offering of the call. When a call comes in, it is first offered. For some small amount of time, the application may have the option to reject the call using lineDrop, redirect the call to another station using lineRedirect, answer the call using lineAnswer, or accept the call using lineAccept. After a call has been successfully accepted by an application, alerting begins at both the called and calling device and the call state typically transitions to accepted.

Alerting is reported to the application by the LINE_LINEDEVSTATE message with the ringing indication.

The lineAccept function may also be supported by non-ISDN service providers. The call state transition to accepted can be used by other applications as an indication that another application has claimed responsibility for the call and has presented the call to the user.

The application has the option to send user-user information at the time of the accept. Even if user-user information is sent, there is no guarantee that the network will deliver this information to the calling party. An application should consult a line's device capabilities to determine whether call accept is available.


Target Platform Windows
Header tapi.h
Library Tapi32.lib
DLL Tapi32.dll

See also

Accept overview



Supplementary Line Service Functions