User guide

Originating, Answering, and Disconnecting Calls
Chapter 8 Modem Emulation 38
Originating, Answering, and Disconnecting Calls
In the following table, an application requests a TCP session with the Digi device server. The table displays the
responses of the Digi device server and application as they negotiate a TCP connection.
In the following table, the Digi device server receives a request for a connection.
Originating Calls
To send data to a Digi device server, enter the following information for your application replacing the telephone
number with the Digi device server’s IP address and TCP port number. Enter the following command:
ATDT ipaddress:tcp_port#
an example is ATDT 146.135.13.5:50001
Answering Calls
The Digi device server listens on a pre-defined TCP port to receive data. When the Digi device server receives a
call notification (RING) through a serial port to begin a TCP connection, it needs to reply with an ATA or a pre-
configured Auto-Answer to answer the call.
Note: The TCP ports assigned to the serial ports are as follows:
Serial port 1 listens on TCP port 50001
Serial port 2 listens on TCP port 50002
Serial port 3 listens on TCP port 50003
Serial port 4 listens on TCP port 50004
Disconnecting Calls
The TCP connection disconnects by either dropping the DTR signal on the serial port or sending the escape
sequence <P>+++<P> to the Digi device server. <P> represents a one second pause.
Disconnecting Calls-Digi Device Server
The Digi device server sends a NO CARRIER response to the serial port when the network connection is
dropped.
Application AT Command Digi Device Server Response Notes
AT&F OK. AT command request to restore defaults to factory settings-
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
ATH NO CARRIER response sent Disconnect AT command is sent-Digi device server
responds with NO CARRIER
AT Command Digi Device Server Response Notes
RING The Digi device server sends a Call Notification
ATA (or ATS0=n) CONNECT 115200 Manual (ATA) or Auto Answer (ATS0=n) response-the Digi
device server sends a CONNECT message when the TCP
session is started
NO CARRIER The Digi device server sends a NO CARRIER message
when the remote disconnects