Overview
One method of connecting to a device and communicating with it is via a TCP/IP connection. Often Port servers are used closer to the devices in the field to convert the TCP/IP communications to Serial for connectivity over Ethernet networks. A TCP/IP link may extend from the machine running ACM all the way to the field device, or it may cover part of the distance and then get converted to a serial connection using hardware such as a port server, terminal server or radio.
TCP/IP ports use socket connections to communicate with field devices. When using TCP Listen, socket connections are opened when polling is required and closed when it is complete. The connection to the end device is not kept open when polling is not required. This port type is a good selection when a communication link to a remote device must be shared between multiple applications. It is also a good selection when the polling frequency is relatively slow. To handle cases where field devices can originate the communication, the TCP Listen module can be configured to listen for incoming socket connections. When incoming socket connection requests are detected, the module will accept the connection and perform any necessary communication with the field device.
Logical ports are defined within ACM to represent a communication method used to connect to a device. Each logical port (Port) has a name that is used to reference it. Whenever a port is used, all of the settings defined by that port are used for communications. Multiple devices and/or multiple device types in ACM can share a single port for communications.
Helpful Links
Supported Features
- Releases connections between poll intervals.
Configuration
Once a port has been added to the ACM server, the port must be configured by editing the created object. Configuration may be accomplished using the default Form view.
General, Options Tab
The common attributes for all port are covered in Common Port Configuration.
Port Tab
Connection Type
The type of connection to establish with the remote address.
- TCP (default)
- UDP
- Select UDP Receive Port Default = not selected. Select to use a specific UDP port instead of allowing Windows to select the port.
- UDP Receive Port Default = 0. The local port to use for receiving UDP communications.
Max Sessions
The maximum number of allowable concurrent socket connections. Default = 1. If multiple devices come due for a poll the TCP Listen port object will poll up to this many devices at a time. As some devices finish polling, others that are still waiting will be added to the active polling list - up to the number configured as the max session.
Port Release Delay
The length of time in milliseconds to keep control of the port after communication is done.
Listen Port 1-8
TCP or UDP port number to listen on. These ports are used to 'listen' for incoming connection requests from field devices that can initiate communication. (Select Enable to enable this port)
Enable Dialup Modem
Use a modem when communication through this port.