Fragmenting Of Send Data - Omron NJ501-1300 User Manual

9 Socket Service
SktTCPConnect Instruction
• Execution of the Socket Function
Connect()
The connection is established by
the normal completion of the
SktTCPConnect instruction.
SktTCPSend Instruction
• Execution of the Socket Function
Send()
The data is stored in the send
buffer by the normal completion of
the SktTCPSend instruction.
SktClose Instruction
• Execution of the Socket Function
Close()
The acknowledgment (ACK) of
FIN from the remote node is
received by the normal comple-
tion of the SktClose instruction.
However, RST (not FIN) is sent if
the Linger Option is specified.
9-2-2

Fragmenting of Send Data

The receive buffer for the built-in EtherNet/IP port is a maximum of 9,000 bytes per handle. Up to 16
handles can be used at the same time. If any data that is larger than 9,000 bytes is received, any data
over 9,000 bytes is discarded. Up to 2,000 bytes can be received for a single request. In this case, the
data is sent in fragments as described below.
Using TCP
The conditions shown in the following figure occur when data is sent in fragments in TCP communica-
tions.
(1) A send request is sent from the user program at the sending node. It specifies a vari-
able with a data length of 2,000 bytes.
(2) The built-in EtherNet/IP port separates the send data into 1,024 bytes in data A and
976 bytes in data B.
(3) Data A and data B are sent in sequence by the sending node.
(4) After data A is received, the remaining data B is received.
9-4
Client
Socket
Connect SYN
SYN ACK
Instruction
completed.
ACK
Send
Instruction
completed.
ACK
Close
FIN
ACK
Instruction
completed.
NJ-series CPU Unit Built-in EtherNet/IP Port User's Manual (W506)
Server
Socket
Bind
SktTCPAccept Instruction
Listen
• Execution of Socket Functions
Socket(), Bind(), Listen(), and
Accept
Accept()
• Timeout monitoring until Connect is
completed
The connection is established by the
normal completion of the SktTCPAc-
cept instruction.
Instruction
completed.
SktTCPRcv Instruction
Recv
• Execution of Socket Function Recv()
• Timeout monitoring until data is
received from the remote node
Writing the received data to the variable
is completed by the normal completion
of the SktTCPRcv instruction.
Socket interface
Packets sent by the TCP/IP layer
Packets sent by higher layers