Mitsubishi Q00JCPU User Manual page 532

7
COMMUNICATION
PORTS OF CPU MODULE
7
- 18 7.4 MC Protocol Communication
USING
(e) Response message receive processing
Figure 7.20 shows an example of the response message receive processing on
the external device side.
Communication processing
on the external device side
Request message send processing
Response message receive processing
Is TCP connection open?
Receive the rest of
response messages.
been received within the
The receive data exceeds
the size limit.
Check the receive data size.
Processing for response messages
for all received messages
Figure 7.20 Example of the response messages receive processing on the external device side
Remark
Personal computers use the TCP socket functions internally for Ethernet
communication.
These functions do not have boundary concept. Therefore, when data is sent by
executing the "send" function once, the "recv" function needs to be executed
once, twice or more to receive the same data. (One execution of the "send"
function does not correspond to one execution of the "recv" function.)
For this reason, receive processing described above is required on the external
device side.
If the "recv" function is used in blocking mode, data may be read by executing the
function once.
BUILT-IN
TCP connection is closed.
Has the data
The monitoring timer has run over.
monitoring timer?
Has processing
completed?
End
ETHERNET
The response message
for the following request
has been received.
Error processing