User`s guide

1: Introduction
DC 900-1339H 21
1.2 Freeway Client-Server Environment
The Freeway server acts as a gateway that connects a client on a local-area network to a
wide-area network. Through Freeway, a client application can exchange data with a
remote data link application. Your client application must interact with the Freeway
server and its resident ICPs before exchanging data with the remote data link applica-
tion.
One of the major Freeway server components is the message multiplexor (MsgMux)
that manages the data traffic between the LAN and the WAN environments. The client
application typically interacts with the Freeway MsgMux through a TCP/IP BSD-style
socket interface (or a shared-memory interface if it is a server-resident application
(SRA)). The ICPs interact with the MsgMux through the DMA and/or shared-memory
interface of the industry-standard bus to exchange WAN data. From the client applica-
tion’s point of view, these complexities are handled through a simple and consistent
data link interface (DLI), which provides
dlOpen, dlWrite, dlRead, and dlClose func-
tions.
Figure 1–3 shows a typical Freeway connected to a locally attached client by a TCP/IP
network across an Ethernet LAN interface. Running a client application in the Freeway
client-server environment requires the basic steps described in Section 1.4.
Figure 1–3: A Typical Freeway Server Environment
Freeway
ICP0
ICP1
ICP2
ICP3
TCP/IP
client1
192.52.107.99
freeway2
192.52.107.100
DLI
Client
Application
TSI
TSI
Msg
Mux
Ethernet
WAN
Protocols
TCP/IP
Socket Interface
Client
3125
Standard Bus
Industry
SRA
Shared Memory
Interface