status.i4.v = ntv_check_request(reply_id.u2.r [,message_len.i2.r]
					[,node.i2.r] [,flags.i1.r]
					[,request_id.u2.r] [,source.i1a.r]

	Check the receive buffer for the arrival of a request or USM.
	This routine will return immediately with NET__PENDING (0) if
	the receive buffer is unlocked (no message has arrived).

	reply_id	word in which the reply identification code of
			the message (if any) is returned.

	[message_len]	word in which the length of the message (if any) is
			returned (length is in words).

	[node]		word in which the destination logical trunk and node
			of the message (if any) is returned.
			The trunk (also known as the LAN id) is stored in
			the upper byte of this word.

	[flags]		byte in which the message flags of the received message
			(if any) are returned.  This is a structure of type
			(UAB_M_MULTRPY -> multiple-reply message type,
			 UAB_M_MSGTYPE -> message type code field,
			 UAB_M_TOOLONG -> message is too long for buffer,
			 UAB_M_CANCEL  -> cancel an outstanding multiple-
					  reply message connection)

	[request_id]	word in which the request identification code of the
			received message (if any) is returned.

	[source]	word (2 byte array) in which the source node and logical
			task id are returned (task id in the second byte).

       [client_node]   word in which the logical trunk and node that send
                       the message is returned

	status		VMS completion condition code.

	The values of the arguments only have meaning if the returned
	completion code is not NET__PENDING (0).

	This function returns status values as follows:

	NET__PENDING	receive buffer empty and unlocked (value is 0).
	SS__NORMAL	receive buffer is locked by a request or a new USM
	NET__NOTCNCT	not connected
	NET__NOTRUM	not connected to receive unsolicited messages
	NET__REQTRUNC	request truncated

	This function requires the following include files:

	acnet_h, ssdef_h

	Related functions:

	ntv_wait_request, ntv_receive_request