Notes On Flow Control (Hardware/Software Handshaking); Notes On Router Setup - Elk IP232 Installation And Configuration Manual

Notes on Flow Control (Software/Hardware Handshaking)
When serial devices transfer large amounts of streaming data, sometimes the sending device can get ahead of the
receiving device. Without any method to slow or stop the sender, the receiver may lose or drop some of the data.
Flow Control is a method for telling the sender to stop until receiver can catch up.
There are two types of flow control, hardware and software. Hardware flow control uses two or more wires between
devices as signals to stop and resume sending. Before the receiver becomes overwhelmed it signals the sender
using one of the lines. This requires the serial cable to be wired properly to include those lines. They are labeled
RTS and CTS. Software flow control on the other hand, does not require extra wires in the cable. The receiver
sends a special byte, called "XOFF" to tell the sender to stop. When ready, it sends an "XON" byte to resume. Of
course, this means the serial data being transferred cannot contain XON or XOFF bytes in the data stream or else
the device receiving those bytes will spuriously stop and resume sending.
You should use flow control only if you understand how it works and if the connected device requires it.

Notes on Router Setup

The table below lists the ports used by the ELK-IP232.
Port Protocol
2362 UDP
2401 TCP
(default)
Port Forwarding
The TCP-IP Port used for accepting connections should not be routed outside the local network for security
reasons. However, if you understand the risks and have a need to route the port outside, it is possible to do so.
By default, the port is 2401, although this may be changed using the Configuration Utility. This port must be
opened through the router to allow access to the ELK-IP232 through the Internet. You must access the router's
setup in order to open (port forward) these ports. The method for this differs from product to product. Some routers
use a software utility to access their setup while others can be accessed via a web browser. Consult the router's
documentation for complete instructions on this procedure. Because of the variety of routers available, Elk
Products Technical Support will be unable to assist you with this.
Page 8
Use
Discovery (Search)
Bridged connections
Routing
Do not route outside local network
Not recommended to route outside local net
ELK-IP232 Installation and Configuration Manual