In addition to its most common use as a "nailed-up RS-232 pipe" when used in pairs, the Etherpath serial server is often used to provide remote serial port access for a computer connected through the TCP/IP network. There are several different methods to use software to complete this connection. We'll discuss the most common approaches and give some examples of code and program packages that are freely available or can be purchased at reasonable cost. The major categories (in order by ease of implementation) are...

1. Manual telnet access to the Etherpath
2. Scripted telnet access to the Etherpath using standard communications software
3. Port redirector software
4. Custom-written application software

Manual telnet

The easiest way to access the remote serial port is to simply telnet to the Etherpath from a workstation. Once the telnet session is established, all keystrokes are passed through to the Etherpath serial port and any data incoming on that port is passed to the screen of the workstation computer. This is the method most often used for casual access to remote management ports on equipment such as PBX machines, routers, datacom equipment, seldom-used host computers, and other devices that require plain terminal access. For MSWindows users, Windows is installed with a program, telnet.exe, that can be used; or commonly used terminal emulation programs are available such as Procomm, Hyperterm Pro, etc. All unix machines are supplied with a telnet program.

Scripted Telnet

Using the same telnet programs, a script (or batch file) is written to automate the process. This script file may be used to connect to the remote device, cause some control commands to be sent, or read status and log it to a disk file. The Windows programs we have the most experience with are Procomm's ASPECT scripting language, and WRQ's Reflection series scripts. On Unix machines, shell scripts are used with bash or other shells, or more capable scripting languages are used such as perl.

Port Redirector SoftwareWhen PC or Unix application software must access the remote device through an Etherpath connection, and the software can not be modified for TCP/IP communications, the most straight-forward method is to use port redirection software. A port redirector program tricks the computer into thinking that the remote port is actually a local COM: port. This software would be run on the computer workstation, then the application software reads and writes to the COM: port normally... none the wiser. This approach is commonly used with proprietary software that the customer either can't change because of technical or economic factors.

DCB tested a number of port redirector packages, and recommends only a couple. The program of choice for Microsoft Windows (all versions) is Serial/IP by Tactical Software (Download a 30 day trial copy here). This program creates a remote COM: port on the Windows PC that is accessable just like your local physical ports (up to 255 remote ports are available). This excellent package runs on all varieties of Microsoft Windows. After trying it, you can purchase a license for Serial/IP from DCBI f instead, you wish to use DDE connections directly into a spreadsheet or equivalent, TCPWedge, sold by TAL Technologies ( http://www.taltech.com ) is also a quality product, but it doesn't create clean, virtual COM: ports. It's about $200 to $400. They also have a demo version available for download.

Custom Software

For specific applications, it makes sense to write a custom program to communicate with the Etherpath. A number of DCB's OEM customers choose this method. For example, if you are using the Etherpath so your alarm system can communicate with remote alarm panels or door release units, the program running on the host computer can be programmed to communicate directly with the Etherpath using TCP/IP network programming.

see Etherpath specifications sheet