Multitech MMCModem GPRS (MTMMC-G) Instrukcja Użytkownika Pobierz pdf (Strona 25)

Chapter 4 – Data Exchange for Protocol Services

Multi-Tech Systems, Inc. IP Connectivity AT Commands for GPRS-F4 Wireless Modems (PN S000437C) 25

Socket Data Exchange +WIPDATA

Description: The +WIPDATA command is used to read/write from/to a socket. On successful

execution of the command, the UART switches to data mode. The UART can be

switched back to AT mode by sending “+++” with 1 second guard time before and

after the sequence. If data is not read using +WIPDATA command, further data will

be delayed.

An unsolicited event is received when there is a data to read on socket.

Data can be sent on the sockets using two modes

• continuous mode

• continuous transparent mode

Description Notes:

• The SIM card must be inserted in order to use this command

• The PIN 1/ CHV 1 code must be entered in order to use this command.

• The PIN 2/CHV 2 code does not have to be entered in order to use this

command.

• The +WIND general indication command value from which +WIPCREATE

is allowed is 4. This value (4) indicates that the product is ready to process

AT commands (except phonebooks, AOC, SMS), but is still in emergency

mode. See Appendix A – GSM/GPRS +WIND AT Command.

Continuous Mode: TCP Sockets in Continuous Mode

In continuous mode, an [ETX] character is considered as an end of data. When an

[ETX] character is sent on the mapped UART, the TCP socket is shutdown and the

peer side is informed of this shutdown with the indication

"[CR][LF]SHUTDOWN[CR][LF]" on the mapped UART.

In case an [EXT]/[DLE] character needs to be transmitted as data, it should be

preceded by a [DLE] character. Similarly, [EXT]/[DLE] characters received by the

TXP/IP stack from the Internet are sent to the host through the serial port preceded

by a [DLE] character.

To close sockets, switch the UART to AT command mode and use the

+WIPCLOSE command.

UDP Sockets in Continuous Mode

UDP is a connectionless protocol, and, hence, there is no way to detect or cause a

shutdown. However, an [ETX] character is used to mark the boundaries of

datagrams.

All data written on an UDP socket is collected till an [ETX] character is encountered

or the maximum size of the datagram

is reached and will be sent as a single

datagram. Similarly when reading data, all data will be read till an [ETX] character

is encountered which indicates the end of the datagram.

Maximum size of an UDP datagram has been fixed to 5840 Bytes. This limit

is an arbitrary one. Nevertheless, note that smaller the datagram is the surer it

will reach the aimed destination. Note that UDP is not a reliable transport layer.

In case an [ETX]/[DLE] character needs to be transmitted, it should be preceded by

[DLE] character similar to TCP socket.

When the UART leaves DATA mode, either because of “+++” escape sequence or

because of an AT+WIPDATA=1, index, 0 on another UART, the currently unsent

data are sent as a single datagram.

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