User manual

Chapter 7 Special Features: Modem Emulation 45
DSR and DTR on the serial device side are connected to the DSR signal of
the Digi device.
Scenarios for Modem Emulation
Outgoing Modem Emulation Connection
Serial device sends ATDx.x.x.x:y command, which triggers the device
server to establish a telnet connection to destination IP=x.x.x.x, port=y.
Incoming Modem Emulation Connection
A device on the network telnets to port 50001 (50000+1 = 1st serial port).
This incoming connection triggers the device server to generate a RING on
the serial port. The device attached to the serial port will answer the RING
and the connection is established.
Modem Emulation Pooling
This is a combination of Incoming Modem Emulation Connection and a
hunt group. A device on the network telnets to port 50000. The device
server checks if a serial port configured for modem emulation is available.
If so, it connects to the port, otherwise returns an error.
Modem Emulation Bridge
A combination of Outgoing and Incoming Modem Emulation Connections,
in which both serial devices require to talk to a modem. The first serial
device telnets to the second device using ATDx.x.x.x:y, the second device
gets a RING and accepts the incoming telnet connection.
Originating, Answering, and Disconnecting Calls
In the following table, an application requests a TCP session with the Digi
device. The table displays the responses of the Digi device and application
as they negotiate a TCP connection.
DCD (in) DTR (out)
TX (out) RX (in)
RX (in) TX (out)
GND GND
Serial Device Digi Device
Application AT Com-
mand
Digi Device Server Response Notes
AT&F OK.
AT command request to restore defaults to factory set-
tings-Digi device server responds OK.
ATDT ipaddress:TCPport#
Receives request to start a
TCP session. CONNECT
115200.
Request to start TCP session with IP address and TCP
port number of the Digi device server-Digi device server
starts a TCP session
<P>+++<P> OK
Escape sequence is sent <P> is Pause in seconds with
“+++” being the escape sequence in ASCII characters -
Digi device server switches from AT command to data
mode