Filter
Top Products
Chapter 9 Modem Emulation 35
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
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
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