ProSoft Technology MVI71-GEC - Manual (Page 64)

Reference MVI71-GEC ♦ PLC 5 Platform
User Manual Generic ASCII Ethernet Communication Module
Page 64 of 86 ProSoft Technology, Inc.
May 11, 2011
The MVI71-GEC module servers 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 server will close the
connection. If the parameter is set to 0, the server will not perform the timeout
logic and the socket will never be closed by the server 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 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 input 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:
Server Status Data Description of Server
Server 0 IP of Host (192.168.0.100) Port of
Host (1243) State = 1
This server is connected (State=1) to IP
address 192.168.0.100 on TCP port 1243.
Server 1 IP of Host (192.168.0.100) Port of
Host (1244) State = 1
This server is connected (State=1) to IP
address 192.168.0.100 on TCP port 1244.
Server 2 IP of Host (192.168.0.101) Port of
Host (56443) State = 1
This server is connected (State=1) to IP
address 192.168.0.101 on TCP port 56443.
Server 3 IP of Host (192.168.0.102) Port of
Host (7943) State = 1
This server is connected (State=1) to IP
address 192.168.0.102 on TCP port 7943.
Server 4 IP of Host (0.0.0.0) Port of Host (0)
State = 0
This server is not connected (State not equal
to 1) and is waiting for a connection.
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.