Protocol Communication Type; For Tcp/Ip; For Udp/Ip; Precautions For Passive Open - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

Protocol communication type

The packets sent to the external device when a processing is executed and the external device's receive packets are
registered in the protocol.
The packet elements set with the predefined protocol support function are the data section of the packets that are actually
sent and received.
This section describes an example of the packet configuration. For details on the packet elements, refer to the following.
Page 395 Operation Image and Data Structure of Predefined Protocol

For TCP/IP

Destination Sender's MAC
MAC address: address:
6 bytes 6 bytes
Ethernet header

■Precautions for Passive open

• When the CPU module is connected to external device in Passive open state, the IP address of the connected external
device or port number of the external device can be obtained with the SP.SOCCINF instruction.

For UDP/IP

Destination Sender's
MAC address: MAC address:
6 bytes 6 bytes
Ethernet header
With the predefined protocol support function, data is exchanged with the external device with the procedures (communication
type) shown below.
For details on the communication type operation, refer to the following.
Page 395 Operation Image and Data Structure of Predefined Protocol
Communication type
Send only
Receive only
Send & receive
■Precautions for UDP/IP communications
• Use the SP.SOCCSET instruction to change the external device by the CPU module.
■Precautions for broadcast communications
• When the CPU module receives data by receiving the broadcast, the IP address of the external device which send data and
port number of the external device can be obtained with the SP.SOCCINF instruction.
1 FUNCTIONS
40
1.3 Communications Using the Predefined Protocol
Header
Type: IP: TCP:
2 bytes 20 bytes 20 bytes
TCP/IP header
Header
Type: IP: UDP:
2 bytes 20 bytes 8 bytes
UDP/IP header
Description
The send packet is sent once.
If there is a packet that matches within the maximum of 16 registered receive packets, the packet is received.
After sending the send packets, if there are packets that match the up to 16 registered receive packets, the packets are
received.
Maximum data length: 2046 bytes
Data
Maximum data length: 2046 bytes
Data