Appendix B – Detailed Examples
Multi-Tech Systems, Inc. AT Commands for Wireless Modems with IP Connectivity (S000333D)
52
Command Mode / Data Mode for TCP Services: ETX is a character
When DLEMODE is set to 0, no specific process is needed on [ETX] characters.
It means that it is not possible for a host to request an end of connection or to receive a clear indication of end of
connection from the modem.
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 can't end the DATA mode.
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 not preceded by the [ETX]
character)
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 can't end the DATA mode.
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 not preceded by the [ETX]
character)
Socket TCP service :
TCP socket through
AT#LTCPSTART or
AT#OTCP
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.
[ETX] is CTRL+C in a keyboard.
[DLE] is CTRL+P in a keyboard.
