Multitech GPRS Bedienungsanleitung PDF herunterladen (Seite 31)

Chapter 5 – TCP Socket Services

Multi-Tech Systems, Inc. AT Commands for Wireless Modems with IP Connectivity (S000333B) 31

#OTCP Open TCP Connection

Definition: This command sent by the attached host directs the TCP/IP stack to open a TCP connection to the

specified TCP server. Once an IP link is established, the attached host can open a TCP connection at

any time (except when the TCP/IP stack software is already in a process using TCP resources).

This TCP connection may be closed by the remote TCP server or by the attached host via sending an

ETX character on the serial port (depending on the DLEMODE parameter).

DLEMODE Value Notes:

Depending on the DLEMODE value, the attached host may close this TCP connection by sending an

ETX character.

• If the DLEMODE parameter is set to 1, the TCP/IP stack will only interpret an <ETX> character

as a close request if it’s not preceded by a <DLE> character. As a consequence, the attached

host must send <ETX> characters preceded by <DLE> characters, and it must also code

<DLE> characters in <DLE><DLE>. Similarly, each <ETX> character present in the payload

data of the TCP frame will be coded by the TCP/IP stack on the serial port as <DLE><ETX>.

Each <DLE> character will be coded as <DLE><DLE>. The attached host must then decode

the TCP socket flow to remove these escape characters.

• If DLEMODE is set to 0, the host cannot close the TCP connection (unless an error occurs).

If the remote TCP server closes the connection, the TCP/IP stack sends an ETX character on the serial

port.

Values: Read Parameters:

DLEMODE

TCPPORT

TCPSERV

Syntax: AT#OTCP

Command Possible Responses

AT#OTCP

Request

TCP

socket

open

OK_Info_WaitingForData

Note: This message signals that the TCP socket has been opened.

All the data from the attached host / remote TCP server is then immediately

transferred by the TCP/IP stack to the remote TCP server / attached host.

Depending on the DLEMODE value, the attached host may close this TCP

connection by sending an ETX character. If the remote TCP server closes the

connection, the TCP/IP stack issues an ETX character on the serial port.

OK_Info_SocketClosed

Note: The TCP socket is closed.

AT#OTCP #CME ERROR: 38027

Note: The address of the FTP server has not been resolved by the secondary DNS

server.

TCP/IP stack is not able to reach the primary and secondary DNS servers or a

wrong FTP server address has been filled in.

AT#OTCP #CME ERROR: <value>

Note: An error has occurred during the TCP connection. This connection is being

closed.

If this error occurs once the TCP connection opened, it is preceded by an ETX

character

See section ‘Response messages and error codes’.

#VTCP Display TCP Parameters

Definition: This command directs the TCP/IP stack to display all the AT# parameters related to the TCP socket

configuration.

Values: Read Parameters:

DLEMODE

TCPPORT

TCPSERV

Syntax: AT#VTCP

Command Possible Responses

AT#VTCP

Note: View TCP parameters

#DLEMODE: 1

#TCPPORT: “”

#TCPSERV: 0

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