Multitech MTCBA-G-F2 Manual de usuario descargar pdf (Pagina 54)

Appendix B – Detailed Examples

Multi-Tech Systems, Inc. AT Commands for Wireless Modems with IP Connectivity (S000333D) 54

Configuring Flow Control over the Serial Port

The following description explains how to configure flow control for communication between the modem and the attached

equipment.

Description: The flow control is managed by the software. It is configured through the AT command: AT+IFC

Using the DNS Service

This example shows how to use the DNS client embedded in the modem in order to use symbolic names instead of IP

addresses.

Description: The DNS servers available on the Internet or within an Intranet are used to resolve a symbolic

hostname (like mail.domain.com) into an IP address (192.168.255.250).

DNS provides a means of using user-friendly and easy to remember names for email, TCP, FTP

servers rather than using the standard IP addressing format. Moreover these servers can switch to a

different IP addressed destination without requiring any change on the symbolic name configuration.

Configuration:

Primary DNS The IP address of the primary DNS server must be stored in dotted decimal notation

(xxx.xxx.xxx.xxx).

This address is generally provided with your ISP subscription.

Note: the modem does not currently offer the possibility to get this address during PPP

negotiation.

AT#DNSSERV1

Secondary DNS The IP address of the secondary (backup) DNS server must be stored in dotted decimal notation

(xxx.xxx.xxx.xxx). This parameter is optional for running the DNS service but provides better

reliability of this service (providing a secondary source of DNS resolution if the primary source

fails for some reason).

This address is generally provided with your ISP subscription. The modem does not currently

offer the possibility to get this address during PPP negotiation.

AT#DNSSERV2

Operation:

Error codes Whenever the modem is unable to reach the primary DNS server or when the primary DNS

server informs the modem that it can't resolve a symbolic hostname into an IP address, the

modem then automatically tries to contact the secondary DNS server.

Whenever the modem can't reach the secondary DNS server or when the secondary DNS server

informs the modem that it can't resolve a symbolic name into an IP address, a ‘#CME ERROR:

38027’ message is sent on the serial port.

Note:

In the case of GPRS, the DNS server addresses are provided by the GPRS operator on successful network connection of

the module. The addresses provided are used in place of DNSSERV1 and DNSSERV2. (The DNS address parameters

are not updated for display purposes). If no addresses are provided, the DNSSERV1 and DNSSERV2 parameter

addresses are used as in GSM.

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Multitech MTCBA-G-F2 Manual de usuario Pagina 54