Appendix B – Detailed Examples
Multi-Tech Systems, Inc. AT Commands for Wireless Modems with IP Connectivity (S000333D)
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Command Mode / Data Mode for TCP Services: [ETX] means END of TCP connection
When DLEMODE is set to 1, the [ETX] character means a request or an indication of end of connection.
As a consequence, [ETX] characters that belongs to the payload data must be sent by the host on the serial port
preceded by a [DLE] character. Similarly [ETX] characters received by the modem from the Internet are sent to the host
through the serial port preceded by a [DLE] character
Socket TCP service :
TCP socket through
AT#LTCPSTART or
AT#OTCP
ENTRY FLOW
Enter in DATA mode:
The “Ok_Info_WaitingForData” message
sent to the host on the serial port indicates
the entry in DATA mode.
The modem is ready to receive the data from
the host.
This data will be sent to the remote TCP
peer.
Exit DATA mode:
1. The host ends the DATA mode by sending the
[ETX] character (not preceded by [DLE]) on
the serial port.
2. The modem ends the DATA mode if an error
occurs or if the TCP peer disconnects by
sending an error message to the host (this
message is preceded by the [ETX] character)
[DLE] is CTRL+P in a keyboard.
[ETX] is CTRL+C in a keyboard.
Socket TCP service :
TCP socket through
AT#LTCPSTART or
AT#OTCP
OUTPUT FLOW
Enter in DATA mode:
The “Ok_Info_WaitingForData” message
sent to the host on the serial port indicates
the entry in DATA mode.
The modem then immediately sends the
data received from the remote TCP peer to
the host.
Exit DATA mode:
1. The host ends the DATA mode by sending
the [ETX] character (not preceded by [DLE])
on the serial port.
2. The modem ends the DATA mode if an error
occurs or if the TCP peer disconnects by
sending a message to the host (this message
is preceded by the [ETX] character)
[ETX] is CTRL+C in a keyboard.
[DLE] is CTRL+P in a keyboard.
