Appendix E: External Server And Remote Services - ControlByWeb WEBRelay-10+ User Manual

Appendix E: External Server and Remote Services

Note: The following methods are supported by WebRelay-10 Plus™; however, Xytronix Research & Design, Inc.
does not provide or support custom third party applications, or external web servers.
Accessing WebRelay-10 Plus™ with Custom Software or Third
Party Applications
WebRelay-10 Plus™ provides a programming interface that allows applications running on a computer
to have full access to it. Custom applications can send commands to WebRelay-10 Plus™ for monitoring
and control. They can also be used to provide a custom user interface, provide access to multiple units in
a single screen, and allow for automation, logging, etc.
Using an External Web Server
Rather than accessing WebRelay-10 Plus™ directly from a computer, an external web server can be
used. The term "external" web server is used here to mean a separate web server (such as Apache
or IIS) that is not the web server built into WebRelay-10 Plus™. In this scenario, users access custom
web pages that reside on the external web server and the external web server communicates with
WebRelay-10 Plus™. This means users would not communicate directly with WebRelay-10 Plus™.
Using an external web server to provide a custom user interface is beneficial because multiple
WebRelay-10 Plus™ devices (or other ControlByWeb™ products) can be integrated into a single
control page or set of pages so they appear as part of a larger system rather than individual devices.
In other words, the user may not be aware that he/she is using multiple ControlByWeb™ devices, but
rather the user sees a custom control page that shows the entire system. In addition, the use of an
external web server allows programmers to create custom user interfaces that take advantage of the
additional resources typically available on larger web servers, including more memory and various web
programming languages.
There are two approaches that an external server can use to communicate with WebRelay-10 Plus™ and
other ControlByWeb™ devices, Direct Server Control and Remote Services.
Direct Server Control
The first approach is for the external server to create a TCP connection whenever it needs to access
WebRelay-10 Plus™. In this case, the external server opens the connection, sends commands and/or
reads the device, and closes the connection.
This method is ideal when the web server and all of WebRelay-10 Plus™ devices are on the same
network (without routers between them). In this case, the server can communicate with WebRelay-10
Plus™ directly and securely since data never has to leave the local network. When the server and
WebRelay-10 Plus™ are on different networks, routers must be configured to allow appropriate access. If
a public network is used, such as the Internet, security precautions should be considered.
Remote Services
The second approach is for WebRelay-10 Plus™ to initiate a connection using the "Remote Services."
The settings under the Advanced Network tab in the setup pages will enable the WebRelay-10 Plus™
to open a TCP connection with an external server. Once the connection is open, the external server can
send commands and/or read the device. The external server can leave the connection open (so that it
never closes) or close the connection.
Xytronix Research & Design, Inc.
WebRelay-10 Plus™ Users Manual
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