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shown in the diagram also applies if a CLOSE REQUEST command is executed
during OPEN REQUEST command execution, with the exception of the status
of the Open Flag.
10-2-6 Precautions in Using Socket Services
•
If a short response monitor time is specified in the CMCR control data and the
PC Card Unit is operating under a high load, a result may be stored even if the
response code indicates a time-out. If this occurs, increase the monitor time
specified with CMCR.
•
If the Results Storage Error Flag turns ON in socket status, it indicates that the
specified results storage area does not exist in the C200HX/HG/HE. Correct
the user program.
•
Communications processing may be slowed down by multiple simultaneous
usage of PC Card Unit functions, or by the contents of the user program.
•
Communications efficiency may decrease due to high communications loads
on the network.
•
All data is flushed from the socket’s communications buffer when a socket is
closed with the CLOSE REQUEST command. In some cases, the transmit
data for the SEND REQUEST command issued just before the socket was
closed may not be sent.
•
When sockets are open, the PC Card Unit internally provides 64 bytes of
receive buffers to allow data to be received at any time. These buffers are
shared by all open sockets. Socket service communications are interrupted if
all these buffers become full. The user application must therefore issue
RECEIVE REQUEST commands frequently enough to prevent the internal
buffers from becoming full.
•
With the UDP socket, data can be broadcasted to all nodes of the network
simultaneously by setting a broadcast address for the destination node
address. The maximum length of broadcast data is 1,472 bytes. Data in multi-
ple fragments (over 1,472 bytes for a UDP socket) cannot be broadcast.
•
The UDP socket does not check the transmitted data to ensure communica-
tions reliability. To increase communication reliability, communications checks
and retries must be included in the user application program.
•
If the TCP socket of the remote node is closed (the connection is broken) dur-
ing communications, the TCP socket at the local node must also be closed.
The communications results storage areas can be used to check if the connec-
tion has been broken. Close the local socket immediately after detecting that
the remote TCP socket has closed. The following situations indicate that the
remote socket has closed.
TCP receive results storage area: response code = 0000 (normal), number
of bytes received = 0000
TCP send results storage area: response code = 0081 (specified socket
closed during transmission)
•
After closing the port of a connected TCP/IP socket, the port cannot be used
within 60 seconds of being closed. However, this restriction does not apply for
a port opened using the TCP OPEN REQUEST (ACTIVE) command with a
local TCP port number of 0 (port number automatically assigned) which is
closed from the side that actively opened the socket.
•
A connection is established for a passively opened socket by actively opening
it from another socket. A connection will not be established for an actively
opened socket even if the active open command is executed from another
socket. Moreover, you cannot actively open multiple connections to a socket
passively opened at the PC Card Unit.
UDP and TCP Socket
Services
UDP Socket Services Only
TCP Socket Services Only
Using Socket Services
Section 10-2
Summary of Contents for SYSMAC C200HW-PCS01-EV1
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