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UDP_RECVL(3)		   libdill Library Functions		  UDP_RECVL(3)

       udp_recvl - receives an UDP packet

	      #include <libdill.h>

	      ssize_t udp_recvl(
		  int s,
		  struct ipaddr* addr,
		  struct iolist* first,
		  struct iolist* last,
		  int64_t deadline);

       UDP  is	an  unreliable message-based protocol defined in RFC 768.  The
       size of the message is limited.	The protocol has no initial or	termi-
       nal handshake.  A single	socket can be used to different	destinations.

       This function receives a	single UDP packet.

       This  function accepts a	linked list of I/O buffers instead of a	single
       buffer.	Argument first points to the first  item  in  the  list,  last
       points  to  the last buffer in the list.	 The list represents a single,
       fragmented message, not a list of multiple messages.  Structure	iolist
       has the following members:

	      void *iol_base;	       /* Pointer to the buffer. */
	      size_t iol_len;	       /* Size of the buffer. */
	      struct iolist *iol_next; /* Next buffer in the list. */
	      int iol_rsvd;	       /* Reserved. Must be set	to zero. */

       When  receiving,	iol_base equal to NULL means that iol_len bytes	should
       be skipped.

       The function returns EINVAL error in the	case the list is malformed:

       o If last->iol_next is not NULL.

       o If first and last don't belong	to the same list.

       o If there's a loop in the list.

       o If iol_rsvd of	any item is non-zero.

       The list	(but not the buffers themselves) can be	 temporarily  modified
       while  the function is in progress.  However, once the function returns
       the list	is guaranteed to be the	same as	before the call.

       s: Handle of the	UDP socket.

       addr: Out parameter.  IP	address	of the sender of the packet.   Can  be

       first: Pointer to the first item	of a linked list of I/O	buffers.

       last: Pointer to	the last item of a linked list of I/O buffers.

       deadline:  A  point in time when	the operation should time out, in mil-
       liseconds.  Use the now function	to get your current point in time.   0
       means immediate timeout,	i.e., perform the operation if possible	or re-
       turn without blocking if	not.  -1 means no  deadline,  i.e.,  the  call
       will block forever if the operation cannot be performed.

       This  function  is  not	available  if  libdill is compiled with	--dis-
       able-sockets option.

       In case of success the function returns size of the  received  message,
       in  bytes.  In case of error it returns -1 and sets errno to one	of the
       values below.

       o EBADF:	Invalid	handle.

       o ECANCELED: Current coroutine was canceled.

       o EINVAL: Invalid argument.

       o EMSGSIZE: The data won't fit into the supplied	buffer.

       o ENOTSUP: The handle does not support this operation.

       o ETIMEDOUT: Deadline was reached.

	      struct ipaddr local;
	      ipaddr_local(&local, NULL, 5555, 0);
	      struct ipaddr remote;
	      ipaddr_remote(&remote, "", 5555, 0, -1);
	      int s = udp_open(&local, &remote);
	      udp_send(s1, NULL, "ABC",	3);
	      char buf[2000];
	      ssize_t sz = udp_recv(s, NULL, buf, sizeof(buf), -1);

       mrecv(3)	   mrecvl(3)	msend(3)    msendl(3)	 now(3)	   udp_open(3)
       udp_open_mem(3) udp_recv(3) udp_send(3) udp_sendl(3)

libdill								  UDP_RECVL(3)


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