Mitsubishi Electric FX5 User Manual page 84

Elements of TCP connection
The following four elements control TCP connections, and only one connection can be established with a unique setting for
these elements. To use multiple TCP connections at the same time, at least one of the four elements must be different.
• IP address of the CPU module
• Port number of the CPU module
• IP address of the target device
• Port number of the target device
Reestablishment of the same connection
Allow 500 ms or more before reestablishing a connection of the same target IP address, the same host station port number,
and the same target port number after closing it.
If the reestablishment is time-critical, it is recommended to change the host station port number on the Active open side.
Checking receive data length
Since no delimiter is provided for TCP communication data, separate data blocks that are sent continuously may be
combined, or data sent all at once may be segmented, on the receiving end. The receive data length must be confirmed on
the receiving end as necessary.
When receiving data on the target device, confirm the receive data length as shown below.
Receive the rest of the message
7 SOCKET COMMUNICATION FUNCTION
82
7.3 Precautions
Receive processing on the target device
Received message receive processing
Is TCP connection
open?
YES
Could data be received
within the monitor timer
value?
YES
Check the received data size
NO
Is receive data-size
sufficient?
YES
Process for the received message
Was the entire
received message
processed?
YES
End
NO
TCP connection is closed
NO
NO
Error handling