Sierra Wireless DART 200 CDPD Modem Dart 200 Cdpd Modem User’s Guide Dart Supported Protocols

DART 200 CDPD Modem User’s Guide 5 DART Supported Protocols

∙Receive locking

∙Backwards compatibility

The details of these options follow.

∙Friends Only Mode - Restricts communication with the modem (for security reasons) to a predefined group of addresses (friends)

This feature is controlled by S-Register 82 which enables and disables the comparison of datagram source addresses against a list stored in the DART 200’s destination dial directory. Refer to the AT&Z command in Modem dial directory, p. 8-24, or Appendix F, DART AT Command Set for details. Only the IP Address portion of the addresses in the dial directory is used with this feature. Bit 0 of S-Register 82 controls this mode. The default is to accept all incoming datagrams (bit 0 = 0).

This bit is significant only when the UDP connection is established passively (server mode). When the connection is established actively (by an ATDP command), incoming datagrams are accepted from the destination address specified in the dial command regardless of the address being in the friends list; this is consistent with basic UDP operation.

In both of the above cases, the source address (IP Address and port number) of the last accepted datagram is saved in a temporary variable for use as the current destination address for all datagrams being sent by the MAS during the current session. This source address information is also saved in S-Register 53 where it can be obtained with an ATS53? command. However, if the application design allows the M-ES to receive messages from multiple clients, outbound datagrams can only be sent to the last source of input data. If this is a potential problem due to timing considerations, refer to the next bullet point on receive locking.

∙Receive Locking - A UDP server feature that allows time for the MAS to respond to a datagram without concern that another datagram from a different source will overlay the current destination address

This feature is controlled by bit 2 of S-Register 82. The default is receive locking disabled (bit 2 = 0). The lock time out period is specified in S-Register 83 in tenths of seconds (default is 3 seconds). If receive locking is enabled, all datagrams arriving after the first one, regardless of their source address, are held in a First-In-First- Out (FIFO) queue until a data transmission occurs, or the time out period expires, releasing the first datagram in the queue.

∙Backward Compatibility - Permits the UDP server to operate in a mode compatible with the basic UDP provided in earlier versions of the software (prior to version 2.0)

PN1197-00 Revision 1.0 5-7