User manual

Chapter 9 Modem Emulation 33
Modem Emulation (Digi One TS and PortServer TS 2/4 MEI only)
Modem emulation enables a system administrator to configure a
networked Digi device server to act as a modem. The Digi device server
emulates modem responses to a serial device and seamlessly sends and
receives data over an Ethernet network instead of a PSTN (Public
Switched Telephone Network). The advantage for a user is the ability to
retain legacy software applications without modification and use a less
expensive Ethernet network in place of public telephone lines.
To use a Digi device server for modem emulation, do the following:
• use a cable with the correct wiring pinouts (see "Modem Emulation
Cable Signals" on page 34)
• configure the serial ports and device type with the Web Interface
Note: Before AT commands are accepted, DSR must go high on the Digi device
server.
Common User Scenarios
The Digi device server in modem emulation mode allows for the easy
replacement of modems in almost any environment where there is a LAN
or WAN.
In Diagram A, the Digi One TS replaces a modem connected to a
workstation running an application. The Digi One TS allows for the use of
software applications without modification by responding to all the AT
commands configured in the workstation application. The Digi One TS
connects to the IP Address of the server when an
ATDT ipaddress:port (ATDT 192.168.25.5:50001)
command is issued. Once the remote device establishes the TCP
connection, a CONNECT message is sent to the serial port and only then
does the Digi device server switch from AT command mode to data mode.
Using the modem escape sequence or dropping DTR on either side
terminates the connection. A DISCONNECT message will be sent to the
Chapter 9
Modem Emulation
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Server
Workstation
Digi One TS
#1
Ethernet
Serial cable
192.168.25.5
User Scenario-Diagram A