DART 200 CDPD Modem User’s Guide | 5 DART Supported Protocols |
This bit is significant only when the TCP connection is established passively (server mode). When the connection is established actively (by an ATDT command), incoming packets are accepted from the destination address specified in the dial command regardless of whether or not it is contained in the friends list.
In both modes of operations, the source address (IP Address and port number) of the last accepted packet is saved in a temporary variable for use as the current destination address for all packets being sent by the MAS during the current session. This source address information is also saved in
TCP communication
To participate in a TCP session the DART 200 must be registered on the CDPD system. Refer to Channel acquisition, p.
A TCP session can be started by the central site system (host or
Unless the application is being run on a closed system, use port numbers between 1025 and 4999 for compliance with industry standards. Alternatively, the dial could reference an IP Address/port stored in the DART 200 dial list by the ATDTSn command where n is the position number of the desired IP Address in the dial list. Refer to the &Z command in Modem dial directory, p.
When a connection with the server is established:
1.The modem enters online mode and presents a CONNECT response to the MAS. It is customary (but not required) for the client to do the first data transmission.
2.The MAS begins data transfer by writing application data to the DART 200 through the
3.This data is assembled until a data forwarding condition occurs, as described in Data forwarding, p.
4.The DART 200 attaches the TCP header and sends the packet onto the network.
