Device #
Connection Status
Local Name
Static IPv4   Static IPv6   Domain Lookup
IP Address
Domain Name
Use FC 5/6 instead of 15/16 for unit numbers (slave addresses) starting at
Use FC 5/6 and 15/16 by count for unit numbers (slave addresses) starting at
Default Poll Period
Quick Help

This page sets up the network address and optional device parameters for a remote Modbus/TCP device that will be linked to for remote input and/or output (via the client read and client write maps). The local device acts as a Modbus master to the remote devices listed here.

Device number simply shows you where you are on the device list. Click "next" and "prev" to scroll through the list. Update parameters as applicable and click Update.

Local name is how you will reference this deivice in the Modbus TCP Client Read Maps and Write Maps. This name is only a local reference.

Select whether your remote Modbus TCP server (slave) has an IPv4 address, IPv6 address, or needs to be looked up via DNS. Enter the applicable IP address or domain name.

Enter a port number. This will default to 502 if left set to zero. Port 502 is the standard Modbus TCP port.

If your slave/server device only supports function codes 5 and 6 for writing, check the Use FC 5/6 box. The default function codes are 15 and 16, which are most widely used. If you check the box, you should also enter a "starting at" unit # or slave address. This allows supporting both types of devices at the same time provided you assign slave addresses in two non-overlapping groups. (These settings do not apply if the gateway is the slave.)

Check "Use FC 5/6 ... by count..." if you have a slave device that requires function codes 5 and 6 for single registers while requiring function codes 15 and 16 for multiple register writes. The same "starting at" requirement applies here.

Enter a default poll period in seconds. This default will be used if no different poll period is given in the individual Read Map or Write Map.

Connection status will show a non-zero error code if there is a socket error. Possible errors include:

5 = Connection attempt timed out, unable to establish connection (usually means remote device not connected or not reachable)
104 = Connection reset by peer
111 = Connection refused
113 = Connection aborted
114 = Network is unreachable
115 = Network interface not configured
116 = Connection timed out
118 = Host is unreachable
125 = Address not available
205 = DNS error