WebRelay-10 Users Manual
Appendix C: Accessing WebRelay-10TM Over the Internet
way, all devices on the LAN share a single public IP address. This is called Network Address Translation
(NAT).
Port Forwarding
The router can be configured to allow outside access to WebRelay-10 and WebRelay™. All requests
from the Internet to any device on the local network must use the public IP address ( 266.70.164.97).
With only a single IP address, TCP ports are used to identify the intended device for the incoming
message.
Using the mailing address analogy, the port is similar to a post office box. The IP address specifies the
location, and the port specifies the specific recipient. Port numbers can be set to any number between 1
and 65235. However, many port numbers are reserved for specific applications and should be avoided.
As a general rule, numbers above 8000 are safe to use. All of the ControlByWeb™ products come from
the factory with the HTTP port set to 80, which is the standard port for HTTP. In this example,
WebRelay-10 HTTP port will be changed to port 8000 and WebRelay™ port will be changed to 8001.
Once the ports are changed in the two ControlByWeb™ devices, the router must be set up for port
forwarding.
Port forwarding associates the IP address of each local device with an assigned port. In this example,
the address 192.168.1.25 for WebRelay-10 would be associated with port 8000. The address
192.168.1.26 for WebRelay™ would be associated with port 8001. WebRelay-10 would be accessed
from the Internet by entering the public IP address of the router, plus the port number assigned to
WebRelay-10 in the URL window of the browser, http://266.70.164.97:8000. All Internet requests to the
router for port 8000 would be forwarded to WebRelay-10. Similarly, all request for port 8001 would be
forwarded to WebRelay.
Note: When an HTTP request comes in to the router without the specific port specified
(http://266.70.164.97), the router will handle this as a port 80 request (default HTTP port). In other
words, http://266.70.164.97 is exactly the same as http://266.70.164.97:80.
Router configuration can vary widely. Some routers have the capability of translating the addresses and
the ports, which would require no port configuration change on the WebRelay. For example, the router
would be configured so that messages sent to
, which is the default HTTP port.
An example screen shot of a router configuration is given below. This setup allows the two
ControlByWeb™ products in the above example to be accessed remotely from the Internet.
Note: This screen shot is simply an example of a typical router setup page. Routers will vary.
Xytronix Research & Design, Inc.
page 85
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