#ifndef _NTLPCAPI_H
// begin_private

/**
 * The NtAlpcConnectPort routine requests a connection to an ALPC port.
 *
 * \param PortHandle Receives a handle to the client-side communication port.
 * \param PortName Name of the port to connect to.
 * \param ObjectAttributes Specifies the object attributes for the client port.
 * \param PortAttributes Defines the operational characteristics of the client port.
 * \param Flags Connection flags.
 * \param RequiredServerSid Optional SID of the server to connect to.
 * \param ConnectionMessage Optional message to send with the connection request.
 * \param BufferLength Optional size of the connection message.
 * \param OutMessageAttributes Optional message attributes sent with the request.
 * \param InMessageAttributes Optional message attributes received with the reply.
 * \param Timeout Optional timeout for the connection request.
 * \return NTSTATUS Successful or errant status.
 */
_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
NtAlpcConnectPort(
    _Out_ PHANDLE PortHandle,
    _In_ PCUNICODE_STRING PortName,
    _In_opt_ POBJECT_ATTRIBUTES ObjectAttributes,
    _In_opt_ PALPC_PORT_ATTRIBUTES PortAttributes,
    _In_ ALPC_MESSAGE_FLAGS Flags,
    _In_opt_ PSID RequiredServerSid,
    _Inout_updates_bytes_to_opt_(*BufferLength, *BufferLength) PPORT_MESSAGE ConnectionMessage,
    _Inout_opt_ PSIZE_T BufferLength,
    _Inout_opt_ PALPC_MESSAGE_ATTRIBUTES OutMessageAttributes,
    _Inout_opt_ PALPC_MESSAGE_ATTRIBUTES InMessageAttributes,
    _In_opt_ PLARGE_INTEGER Timeout
    );

// end_private
#endif
View code on GitHub

#ifndef _NTZWAPI_H

_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
ZwAlpcConnectPort(
    _Out_ PHANDLE PortHandle,
    _In_ PCUNICODE_STRING PortName,
    _In_opt_ POBJECT_ATTRIBUTES ObjectAttributes,
    _In_opt_ PALPC_PORT_ATTRIBUTES PortAttributes,
    _In_ ULONG Flags,
    _In_opt_ PSID RequiredServerSid,
    _Inout_updates_bytes_to_opt_(*BufferLength, *BufferLength) PPORT_MESSAGE ConnectionMessage,
    _Inout_opt_ PSIZE_T BufferLength,
    _Inout_opt_ PALPC_MESSAGE_ATTRIBUTES OutMessageAttributes,
    _Inout_opt_ PALPC_MESSAGE_ATTRIBUTES InMessageAttributes,
    _In_opt_ PLARGE_INTEGER Timeout
    );

#endif
View code on GitHub

// ntfill.h

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwAlpcConnectPort(
    _Out_ PHANDLE PortHandle,
    _In_ PUNICODE_STRING PortName,
    _In_opt_ POBJECT_ATTRIBUTES ObjectAttributes,
    _In_opt_ PALPC_PORT_ATTRIBUTES PortAttributes,
    _In_ ULONG Flags,
    _In_opt_ PSID RequiredServerSid,
    _Inout_updates_bytes_to_opt_(*BufferLength, *BufferLength) PPORT_MESSAGE ConnectionMessage,
    _Inout_opt_ PSIZE_T BufferLength,
    _Inout_opt_ PALPC_MESSAGE_ATTRIBUTES OutMessageAttributes,
    _Inout_opt_ PALPC_MESSAGE_ATTRIBUTES InMessageAttributes,
    _In_opt_ PLARGE_INTEGER Timeout
    );
View code on GitHub