Mitsubishi Electric MELSEC-L Series - TCP;IP Communications; Establishing a Connection

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7.2 TCP/IP Communications
This section describes TCP/IP communications.
7.2.1 Establishing a connection
TCP/IP communications require establishing connections between communication devices. When the server-side
device is in standby status after performing a Passive open process, a connection is established after the client-side
device issues an open request (Active open process) to the server and a response is received.
In TCP/IP communications, the system establishes a connection and checks whether each data has arrived at the
recipient normally, thereby ensuring data reliability. Compared to UDP/IP communications, however, TCP/IP places a
greater load on the line.
Ex.
When the E71 is in Passive open status
Connected device
E71
Open request
Response
Server
Client
Passive open
(passive)
Active open
(active)
Connection