RpcServerRegisterIf2 function (rpcdce.h)

The RpcServerRegisterIf2 function registers an interface with the RPC run-time library.


RPC_STATUS RpcServerRegisterIf2(
  RPC_IF_HANDLE      IfSpec,
  UUID               *MgrTypeUuid,
  RPC_MGR_EPV        *MgrEpv,
  unsigned int       Flags,
  unsigned int       MaxCalls,
  unsigned int       MaxRpcSize,



MIDL-generated structure indicating the interface to register.


Pointer to a type UUID to associate with the MgrEpv parameter. Specifying a null parameter value (or a nil UUID) registers IfSpec with a nil-type UUID.


Manager routines' entry-point vector (EPV). To use the MIDL-generated default EPV, specify a null value. For more information, please see RPC_MGR_EPV.


Flags. For a list of flag values, see Interface Registration Flags.


Maximum number of concurrent remote procedure call requests the server can accept on an auto-listen interface. The MaxCalls parameter is only applicable on an auto-listen interface, and is ignored on interfaces that are not auto-listen. The RPC run-time library makes its best effort to ensure the server does not allow more concurrent call requests than the number of calls specified in MaxCalls. The actual number can be greater and can vary for each protocol sequence.

Calls on other interfaces are governed by the value of the process-wide MaxCalls parameter specified in the RpcServerListen function call.

If the number of concurrent calls is not a concern, you can achieve slightly better server-side performance by specifying the default value using RPC_C_LISTEN_MAX_CALLS_DEFAULT. Doing so relieves the RPC run-time environment from enforcing an unnecessary restriction.


Maximum size of incoming data blocks, in bytes. This parameter may be used to help prevent malicious denial-of-service attacks. If the data block of a remote procedure call is larger than MaxRpcSize, the RPC run-time library rejects the call and sends an RPC_S_ACCESS_DENIED error to the client. Specifying a value of (unsigned int) –1 for this parameter removes the limit on the size of incoming data blocks. This parameter has no effect on calls made over the ncalrpc protocol.


Security-callback function, or NULL for no callback. Each registered interface can have a different callback function. See Remarks.

Return value

Returns RPC_S_OK upon success.

Note  For a list of valid error codes, see RPC Return Values.


The parameters and effects of the RpcServerRegisterIf2 function extend those of the RpcServerRegisterIf function. The difference is the ability to register an auto-listen interface and to specify a security-callback function.

The server application code calls RpcServerRegisterIf2 to register an interface. To register an interface, the server provides the following information:

  • Interface specification

    The interface specification is a data structure that the MIDL compiler generates.

  • Manager type UUID and manager EPV

    The manager type UUID and the manager EPV determine which manager routine executes when a server receives a remote procedure call request from a client. For each implementation of an interface offered by a server, it must register a separate manager EPV.

    Note that when specifying a non-nil, manager type UUID, the server must also call RpcObjectSetType to register objects of this non-nil type.

Specifying the RPC_IF_AUTOLISTEN flags marks the interface as an auto-listen interface. The run time begins listening for calls as soon as the interface is registered, and stops listening when the interface is unregistered. A call to RpcServerUnregisterIf for this interface waits for the completion of all pending calls on this interface. Calls to the RpcServerListen and the RpcMgmtStopServerListening functions do not affect the interface, nor does a call to the RpcServerUnregisterIf function with IfSpec set to the value NULL. This allows a DLL to register RPC interfaces or remove them from the registry without changing the main application's RPC state.

Specifying a security-callback function allows the server application to restrict access to its interfaces on an individual client basis. That is, by default, security is optional; the server run-time will dispatch unsecured calls even if the server has called the RpcServerRegisterAuthInfo function. If the server wants to accept only authenticated clients, an interface callback function must call the RpcBindingInqAuthClient, RpcGetAuthorizationContextForClient, or RpcServerInqCallAttributes function to retrieve the security level, or attempt to impersonate the client with the RpcImpersonateClient function. It can also specify the RPC_IF_ALLOW_SECURE_ONLY flag in the interface flags to reject unauthenticated calls.

When a server application specifies a security-callback function for its interface(s), the RPC run time automatically rejects calls without authentication information to that interface. In addition, the run-time records the interfaces each client has used. When a client makes an RPC to an interface that it has not used during the current communication session, the RPC run-time library calls the interface's security-callback function. Specifying RPC_IF_ALLOW_CALLBACKS_WITH_NO_AUTH flag will prevent the automatic rejection of unauthenticated clients. Note that calls on the so-called NULL security session can have authentication information, even though they come from anonymous clients. Thus the existence of a callback alone is not sufficient to prevent anonymous clients from connecting. Either the security callback function must check for that, or the RPC_IF_ALLOW_SECURE_ONLY flag must be used. RPC_IF_ALLOW_SECURE_ONLY rejects null session calls only on Windows XP and later versions of Windows.

For the signature for the callback function, see RPC_IF_CALLBACK_FN.

The callback function should return RPC_S_OK, if the client is allowed to call methods in this interface. Any other return code will cause the client to receive the exception RPC_S_ACCESS_DENIED.

In some cases, the RPC run time may call the security-callback function more than once per client, per interface. Be sure your callback function can handle this possibility.


Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header rpcdce.h (include Rpc.h)
Library Rpcrt4.lib
DLL Rpcrt4.dll

See also

Registering Interfaces