MVI46-GEC
♦
SLC Platform
Reference
Generic ASCII Ethernet Interface Module
Page 54 of 78
ProSoft Technology, Inc.
April 30, 2008
The MVI46-GEC module servers and clients are configured to handle their
TCP/IP session independently. The user parameter Connection Timeout is
utilized to determine the amount of time a connection can remain idle before the
module's server will close the connection. The module's client also has a
Connection Timeout that is utilized to determine the amount of time a connection
can remain idle before the module's Client will close the connection. If the
parameter is set to 0, the server or the client will not perform the timeout logic
and the socket will never be closed by the server or the client on an idle
condition. If this feature is utilized, it can prevent connections that may be lost
and were not properly closed. For example, if the link between the client and the
server is lost (broken connection), the server will attempt to gently close the
connection after the timeout expires. When no response is received from the
remote client, the server will abort the connection and set up to accept a new
connection. If the connection timeout feature was not utilized in the situation
above, the server will not be available until the TCP/IP stack closes the socket.
Each server on the module is assigned its own server port number. This does not
mean that two or more servers cannot share the same port number. In fact this
might be desirable in some instances. It is up to the ladder logic to keep track of
each message and to insure that a request/response transaction is associated
with the correct connection. Information to keep track of each connection is
passed in each M1 file image. The status data set provides the IP address and
TCP port address for the connection on each server. Each message transferred
between the module and the processor has a server index word. This word
associates the message with a server, which is associated with a connection to a
specific IP address and TCP port address. Therefore, each connection is
specified to the processor by the server index. The following illustration shows a
snapshot of the modules status data:
Ladder logic can send messages to the clients connected to servers 0 to 3.
Messages sent to server 4 will not be sent from the module because there is no
connection active on that server.