User’s Manual Version 1.3
Airolinx Wireless Serial-Ethernet Server
STW-601C
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2. Application
Connectivity
STW provides Tunneling and Virtual COM operation mode. The STW family is designed to transmit data
between one-or-more serial device and one-or-more TCP/IP device through wireless, and hence enhance
the accessibility of the serial device through the ubiquitous TCP/IP based Ethernet. Examples of these
devices are PLC controllers, card readers, display signs, security controls, CNC controller, etc. It has
overcome the limit with a family of STW Series.
2.1 TCP & UDP Protocols
STW can be operated in various Internet Protocols–including two most common protocols: TCP and
UDP.
2.1.1 Transmission
Control Protocol (TCP)
TCP provides a connection and a byte oriented data stream; it is error free, with control parameters such
as flow control, multiple ports option, and order delivery notification. With TCP, networked computers are
connected to one another. Once the connection is established, data can transmit in both directions. TCP
guarantees data sent from one node to be received in the same order by the other node(s). The protocol
also distinguishes the sent data for different applications (such as a Web server or an email server) on the
same computer.
For redundant or dual-network connectivity purposes, STW offers two TCP operation Modes so users may
choose for their specific application: TCP Server Mode and TCP Client Mode.
2.1.2 User Datagram Protocol (UDP)
UDP is a faster datagram delivery protocol. One can configure in the UDP mode on a TCP/IP network to
establish a connection, transmitting multicast data to/from a serial device to one/multiple host computer.
However, UDP does not guarantee the reliability and orderly data streams provided by the TCP mode;
datagram may arrive out of order or go missing without notice; the tradeoff is: UDP is faster and hence
more attractive in time-sensitive applications.
2.2 Connectivity Topology
SE Server is also equipped with Tunneling and Virtual COM operation modes. It is designed to transmit
data among multiple serial devices and among multiple TCP/IP devices on Ethernet, and hence enhances
accessibility of the serial devices immensely. Examples of these serial devices are PLC controllers, card
readers, display signs, security controls, and CNC controllers (See Fig. 1).
Fig. 1. Typical Topology of STW Connection
