RPC_INTERFACE_TEMPLATE structure (rpcdce.h)

The RPC_INTERFACE_TEMPLATE structure defines an RPC interface group server interface.


typedef struct {
  unsigned long      Version;
  RPC_IF_HANDLE      IfSpec;
  UUID               *MgrTypeUuid;
  RPC_MGR_EPV        *MgrEpv;
  unsigned int       Flags;
  unsigned int       MaxCalls;
  unsigned int       MaxRpcSize;
  UUID_VECTOR        *UuidVector;
  RPC_CSTR           Annotation;
  void               *SecurityDescriptor;



This field is reserved and must be set to 0.


MIDL-generated structure that defines the interface to register.


Pointer to a UUID to associate with MgrEpv. NULL or a nil UUID registers IfSpec with a nil UUID.


Pointer to a RPC_MGR_EPV structure that contains the manager routines' entry-point vector (EPV). If NULL,the MIDL-generated default EPV is used.


Flags. For a list of flag values, see Interface Registration Flags. Interface group interfaces are always treated as auto-listen.


Maximum number of concurrent remote procedure call requests the server can accept on this interface. 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. However, the actual number can be greater than MaxCalls and can vary for each protocol sequence.

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

If the number of concurrent calls is not a concern, slightly better server-side performance can be achieved 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, in bytes, of incoming data blocks. MaxRpcSize 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 in MaxRpcSize removes the limit on the size of incoming data blocks. This parameter has no effect on calls made over the ncalrpc protocol.


A pointer to a RPC_INTERFACE_GROUP_IDLE_CALLBACK_FN security-callback function, or NULL for no callback. Each registered interface can have a different callback function.


Pointer to a vector of object UUIDs offered by the server to be registered with the RPC endpoint mapper. The server application constructs this vector. NULL indicates there are no object UUIDs to register.


Pointer to the character-string comment applied to each cross-product element added to the local endpoint-map database. The string can be up to 64 characters long, including the null terminating character. Specify a null value or a null-terminated string ("\0") if there is no annotation string.

The annotation string is used by applications for information only. RPC does not use this string to determine which server instance a client communicates with or for enumerating elements in the endpoint-map database.


Optional security descriptor describing which clients have the right to access the 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.

All interface group interfaces are treated as auto-listen. The runtime begins listening for calls as soon as the interface group is activated. Calls to RpcServerListen and RpcMgmtStopServerListening do not affect the interface, nor does a call to RpcServerUnregisterIf with IfSpec set to NULL.

Specifying a security-callback function in IfCallback 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 RpcServerRegisterAuthInfo. If the server wants to accept only authenticated clients, an interface callback function must call RpcBindingInqAuthClient, RpcGetAuthorizationContextForClient, or RpcServerInqCallAttributes to retrieve the security level, or attempt to impersonate the client with RpcImpersonateClient. It can also specify the RPC_IF_ALLOW_SECURE_ONLY flag in Flags to reject unauthenticated calls.

When a server application specifies a security-callback function for its interface(s) in IfCallback, 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 in Flags will prevent the automatic rejection of unauthenticated clients. Note that calls on the 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 in IfCallback 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. The callback function must be able to handle this possibility.


Minimum supported client Windows 8 [desktop apps only]
Minimum supported server Windows Server 2012 [desktop apps only]
Header rpcdce.h (include Rpc.h)

See also