Udp Socket Interface Notes; Considerations For Tcp Socket - Toshiba V Series User Manual

If the timeout time expires, the "transmission complete timeout (no instruction
response)" error occurs. Since this error has the same code as module failure errors,
first check whether or not the module has failed before attempting to recover from the
error.
(8) User programs specify the time limit until completion for the following three requests
used in socket interface transmission:
• UDP receive request/TCP open request/TCP receive request
If this time limit is exceeded, a "timeout" error occurs. In particular, the EN311 reports
the timeout error to the S controller.
(9) The EN311 uses a priority ordering in processing sockets 1 through 8. Therefore,
systems constructed so that socket 1 is activated frequently may not be able to
process socket 8, resulting in "Transmission completion timeout" errors. When
constructing a system, take the socket utilization conditions into account when
allocating sockets.
Since the send/receive processing for each socket requires about 50 ms,
applications that issue send or receive requests to a given socket should leave an
interval of at least 50 ms times the number of sockets used between each request.
Interval between send (receive)requests to the same socket >= Number of
sockets used ¥ 50 ms
Similarly, the above intervals averaging 50 ms should be left between transmissions
from remote nodes to the local node.
Interval between remote node transmissions >= Number of remote nodes ¥ 50
ms
6.2.5

UDP socket interface notes

(1) In transmission using UDP sockets, the user program must implement any
processing required to assure transmission reliability, such as verifying the reception
of transmitted data and retransmission.
(2) It is possible to broadcast to all nodes on the network using UDP sockets. It is
convenient to prepare a dedicated socket in advance if broadcast transmission is to
be used.
For more information, see the "UDP send request" section and "UDP receive
request" section.
(3) Data transmission between sockets on the same node is not supported.
6.2.6

Considerations for TCP socket

(1) A connection is established by an active open from another socket applied to a
socket in the passive open state. A connection cannot be established by a passive
open from another socket applied to a socket in the passive open state. Similarly, a
connection cannot be established by an active open from another socket applied to a
socket in the active open state. That is, the roles of two sockets for which a
connection is to be established must be determined in advance.
(2) When a passive open is executed, the specified socket is put in the active open wait
state.
If the remote IP address (DIPAddress) and the remote node object socket TCP port
number (DTCP_PORTNO) values are set to 0, the socket will be able to handle
active opens from any remote node.
(3) For a socket in the passive open state, it is not possible to open multiple connections
from other nodes by issuing multiple active open.
(4) Connections cannot be established between sockets on the same node.
6F8C0904
6.2 EN311 Socket Interface Usage Notes
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