INST.No.INE-863B KR2S
【
Communication Interface
】
Instruction Manual
-10-
4-2-3
Disconnection of TCP connection
The communication flow at the disconnection of the TCP connection is as follows.
1. The PC transmits the TCP packet with the FIN flag set to this unit.
2. When this unit receives the FIN packet, it transmits the TCP packet the ACK flag set to the PC.
3. This unit transmits the FIN+ACK packet to the PC.
4. The PC transmits the ACK packet responding to the FIN.
4-2-4
Functions at communications failure
The followings are functions of this unit when the communications failure on the TCP/IP occurs.
In case that there is no response from a communication partner (PC, etc.)
When a response (ACK) packet does not return after this unit transmits data to a
communication partner on Ethernet, this unit repeats to retry transmission (up to about 3
minutes).
When there is no response also to the transmission retry packet, this unit disconnects the TCP
connection.
When the communication partner requests to connect the TCP connection to this unit before
this unit disconnect the TCP connection, this unit transmits the RST packet to refuse the
connection.
In addition, this unit transmits the RST packet in the following cases.
When this unit receives the TCP packet from other than the partner being connected
When this unit receives the RST packet from the communication partner
When this unit receives an unexpected reply packet
Fundamentally, this unit ignores the unexpected reply packet. However, this unit disconnects
the TCP connection as soon as it receives the RST packet in case of forcible disconnection of the
TCP connection by the PC side and so on.
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PC
(Client)
This unit
(Server)
1.
FIN
2.
ACK
3.
FIN+ACK
4.
ACK
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Содержание KR2S
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