Multitech MMCModem GPRS (MTMMC-G) Manual de usuario descargar pdf (Pagina 26)

Chapter 4 – Data Exchange for Protocol Services

Multi-Tech Systems, Inc. IP Connectivity AT Commands for GPRS-F4 Wireless Modems (PN S000437C) 26

Socket Data Exchange +WIPDATA Continued

[ETX] Escaping Mechanism:

The following schematic explains how [ETX] characters, which have a special meaning in

WIPSoft, are handled on the Wavecom Wireless CPU

On transmitting side: When [ETX] characters are not escaped (use case: Desktop PC1

sends data to the Wireless CPU

and the data contains a non-escaped [ETX] (<=> no

[DLE][ETX] sequence), then the [ETX] is not transmitted, but an action is done on the

Wavecom Wireless CPU

regarding the concerned socket:

• UDP socket: A non-escaped [ETX] character marks the boundary of the current

datagram to be sent. The datagram is immediately sent, and the [ETX] is not sent

to the desktop PC2.

• TCP socket: A non-escaped [ETX] character causes a TCP shutdown operation

on the transmitting direction; the peer is informed that the Wavecom Wireless

CPU

will not send any more data on that socket. Usually, the peer will shutdown

the other way (downlink), and this will result in a “peer close event” on the socket.

On receiving side: When [ETX] characters are not escaped (use case: Wavecom

Wireless CPU

sends data to the Desktop PC1 and the data contains a non-escaped

[ETX] (<=> no [DLE][ETX] sequence), then [ETX] means that a special “IP” event

occurred on the Wavecom Wireless CPU

regarding the concerned socket:

• UDP socket: A non-escaped [ETX] signals the boundary of the current received

datagram.

• TCP socket: A non-escaped [ETX] signals that the peer TCP connected to the

TCP unit shutdowns the downlink way. Desktop PC1 should then close the uplink

socket to totally terminate the TCP “session”.

Protocol Mapped UART IP Network (active socket)

UDP Data containing [DLE][ETX] sequence. Data containing [ETX].

UDP [ETX] alone. Mark the boundary of the UDP Datagram received/to

be transmitted.

TCP Data containing [DLE][ETX] sequence. Data containing [ETX].

TCP [ETX] alone. Causes/signals a shutdown operation on TCP socket.

Note that the behavior is symmetrical; i.e., it applies to both the transmitting and receiving side of the

mapped UART.

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Multitech MMCModem GPRS (MTMMC-G) Manual de usuario Pagina 26