Communication via Ethernet CPs in S7 Stations
IP (Internet Protocol)
For internetwork data transmission, the following services are available with suitable CPs such as the CP
S
The
RFC 1006 extends the TCP protocol by allowing the transmission of blocks of data (“messages”) assuming that both partners support RFC 1006.
Transmission reliability is extremely high due to automatic repetition and additional field check mechanisms. The communications partner confirms reception of data and the sender receives a return value on the SEND/RECEIVE interface.
STCP connection
When using the SEND/RECEIVE interface on TCP connections, the Ethernet CP supports the socket interface (for example, Winsock.dll) to TCP/IP found on almost every system (PC or other system).
TCP is intended for reliable internetwork data transmission.
The TCP service complies with the TCP/IP standard (Transmission Control Protocol/Internet Protocol; see /18/).
SUDP connection
UDP is intended for simple internetwork data transmission without confirmation.
If the connection is suitably configured, broadcast and multicast frames can also be sent on UDP connections.
To avoid overload due to high broadcast load, the CP does not allow reception of UDP broadcasts. As an alternative, use the multicast function over a UDP connection. This allows you to register the CP as a node in a multicast group.
SEND/RECEIVE interface
Data transfer is triggered by the user program. The interface to the user program in the SIMATIC S7 is formed by special SIMATIC S7 blocks of the type FC (functions).
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