Toshiba V Series, User Manual

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6.4 Using the EN311 Socket Interface
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• With a connection established, if a no response state from the remote node continues
when data is sent and the EN311 internal resend processing times out (the timeout
time is about 1 minute), the NOACK bit in the socket status will be set to 1. User
programs should close such sockets. Errors will be returned for send/receive requests
issued in this state.
Error status: Timeout error ••• 2848(16#B20)
However, note that the EN311 will return normal complete responses for TCP send
requests issued prior to the timeout, since the send requests from the S controller are
stored internally by the EN311.
When the number of send requests that can be stored is exceeded before the NOACK
bit becomes "1", errors will be returned for that and all following send requests.
Error status: Transmission buffer full ••• 3011(16#BC3)
• One of the following problems may have occurred when there is no response from the
remote node:
• The remote node may have gone down.
• Power may have been lost.
• The remote and local nodes may have become disconnected from the network.
• A send request is seen as completed as soon as it is stored in the EN311. This is done
because the send request should be transmitted later if it is not transmitted
immediately due to network congestions or other reasons when the send request is
executed. A number of send requests that can be stored is three and if no more can be
stored (i.e. when the number of send requests exceeds the EN311 internal storage
capacity), errors will be returned for all further send requests.
Error status: Transmission buffer full ••• 3011(16#BC3)
• The window size of the remote socket may become smaller during the transmission
from the EN311. The TCP send request data size which is requested by the S
controller is larger the window size of the remote node, the EN311 will return an error.
Once it enters this state, TCP send requests will repeatedly cause errors unless the
remote node itself notifies the window size expansion.
In this case, it is recommended to reestablish the connection after closing it.
Error status: Remote node window size is too small ••• 3012(16#BC4)
• Window size: The technique used to notify the available space in the receive buffer of
the local socket to the remote socket. It is possible that the window size becomes
smaller because the receive data has not been processed for some reason or other.
• If the S controller internal completion wait time limit (2 seconds) is exceeded for this
request, the error listed below is returned.
Error status: Send completion timeout ••• 5002(16#EC76)
In this case, first verify that the module is not in the down state by checking the station
status, and then perform the required error handling.
• 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 the following error response:
Error status: Send completion timeout ••• 5002(16#EC76)
• 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