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10.Order info
Product name: Siemens S7-300/400PLC Ethernet Adapter
Product model：ETH Adapter CN
11,Appendix: basic knowledge of Ethernet
TCP / IP transport layer provides two common agreements of TCP and UDP, the two
protocols provide the transmission mechanism of TCP / IP network applications. TCP provides a
guaranteed and reliable information transmission, and UDP use non-guaranteed and non-reliable
method to transmit information.
1.TCP mode
TCP is a guaranteed connection based protocol, before transmitting, the equipment must first
establish duplex connection, disconnect after data transfer is complete. Sending the data need to
receive confirmation of the host then continue sending data, if not received confirmation of the host
or data error, need a certain number of retransmissions. In this way it will be additional traffic, so
slowly than UDP.
TCP communications, including the client (Client) and server (Server), the client take the initiative
to connect to the server, the server can only be a passive client connections, once establish the
connection, the client and server can be duplex data transfer at any time.
Our Ethernet to serial communication module using TCP mode including: TCP Server, TCP Client.
TCP Server (TCP Server) mode:
When the module works in the TCP Server mode, it does not take the initiative to connect to other
devices, but listening on local port, and wait for client connections, if the client can establish a
connection then will go on the duplex communications.
TCP Client (TCP Client) mode:
When the module works in the TCP Client mode, it will take the initiative to connect the setted TCP
server in advance, if the connection is not successful, it will continue to attempt to reconnect, once
the connection success the server will go on the duplex data communications.
2.UDP mode
UDP protocol is unreliable connectionless protocol, data transmission is not required to establish a
connection, do not need to receive confirmation form the host for data transmission, so the UDP
protocol does not guarantee the data sent to the target host packets are received correctly, for high
reliability requirements of the occasion can use the higher level of communication protocol to
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