Settings for TCP Communication

If you have chosen the setting TCP in the Channel field, the TCP Communication tab is ready for input:

Field	Description
Host	Specifies the host name or the IP address of the computer on which PCo is running, for example, `localhost`. Note This entry is only required if you have set `master` as the Modbus type. End of the note.
Port	Specifies the TCP port. The standard port for the Modbus protocol is 502.
Messages in Process	Specifies the maximum number of pending messages. These are messages that have not yet been processed by the connected slave device. You can enter the maximum permitted number of messages here. This always makes sense if communication can also be asynchronous when TCP is used. In asynchronous communication, the Modbus agent does not wait for the response to the last message, but rather already sends the next message. If you enter a higher number of messages here, you can improve performance.
Master IPs	Specifies the list of permitted master devices. You can add as many IP addresses of devices here as you want. This is only possible if you have set PCo as the slave. Since the Modbus protocol does not offer any direct security measures, the list of permitted master devices is the only way of guaranteeing security.