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46 Chapter 7 Special Features: Modem Emulation
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 sends a NO CARRIER response to the serial port when
the network connection is dropped.
Modem Emulation AT Command Set
ATH NO CARRIER response sent
Disconnect AT command is sent-Digi device server
responds with NO CARRIER
Application AT Com-
mand
Digi Device Server Response Notes
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
AT
Command
Function
Result
Code
ATA
Answer command: The Digi Device Server will go off hook and answer a
TCP connection request.