CIE-H12 User Manual Ver. 1.9
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http://www.ezTCP.com
8.2
Connection Problem over Modbus/TCP
Checking parameters related with TCP/IP
When CIE-H12 has a private network IP address, personal computer’s IP address has
to be on the same sub network. Check if the IP address and local port number are
correct. In case of a fixed IP address, the subnet mask, gateway IP address and DNS
IP address should be configured.
Table 8-1 major parameters related with Modbus/TCP
Slave or Master
Local IP Address, the connection mode (Active / Passive), Peer Address and Peer
Port, Subnet Mask, Gateway IP Address, DNS IP Address, DDNS option and etc.
PING Test
Confirm the connection over the network by PING test. If CIE-H12 does not send any
reply from the request, check the network environment.
Firewall
In case the networks which need strong security, the access may be denied by their
firewall. Under this circumstance, users should ask the person in charge of their
network to release ports which will be used. (Ex: TCP 502, UDP 50005)
Operation Mode
A TCP connection is not possible when CIE-H12 is operating in the ISP or Serial
Configuration mode.
Connection Mode
To make a TCP connection, both a server (passive mode) and a client (active mode)
should exist. If there are only servers or clients, the TCP connection cannot be
established.
ezTCP Firewall
When users set the ezTCP firewall with MAC and IP address, any hosts cannot be
reachable to it except for the hosts who have the allowed MAC and IP address.
Inactivate the option or check the setting is correct.
Checking the TCP status
TCP is a protocol connected one to one without multiple connections function except
for using the Multiple-connection. Because of this, if a device is on a TCP connection,
other requests are denied. If users are in this situation, check the network status by
connecting on TELNET or using ezManager.