90
11�1 The Com-Server as TCP server
TCP is a connection-based protocol, i.e. during data transmis-
sion there is a fixed connection between client and server.
TCP possesses all the mechanisms for opening and closing
a connection and ensuring errorless data transfer over the
network.
The connection is controlled by the user program (client
process), which opens (connect()) and closes (close()) the
connection. Once a connection is established, data can be
exchanged bidirectionally between the two processes. The
Com-Server output all the data from the LAN to the serial prot
and in return reads in all the data from the serial port in order
to convey it to your client process.
It must be noted that only one TCP client at a time can be
connected to the serial port of the Com-Server. If there is
already a connection, any attempt from another client is re-
jected until this first connection has been properly closed or
ended by means of a reset.
1
When there is no connection, the entry FREE must
be visible in the Com-Server port menu SETUP Port x r
Port State r Connection State. If a connection is active, the
entry In Use Port number <IP address> appears there.
Application examples TCP-Server mode
• A separate client program should be created for polling
the device serially connected to the Com-Server. TCP sok-
ket communication is supported by all modern program-
ming and script languages.
• The communication program associated with the serial
device offers as a standard feature the ability to specify an
IP address/port number as the destination interface.
To Next Page
Loading...
