CalAmp SMC-CDMA Series, Руководство пользователя

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001-0004-819 Rev01
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Internet Services
The modem has an embedded TCP/IP stack that is driven by AT commands and enables the host
application to easily access the Internet. The advantage of this solution is that it eliminates the need
for the application manufacturer to implement their own TCP/IP and PPP stacks, thus minimizing cost
and time to integrate Internet connectivity into a new or existing host application. Access is provided
to the following Internet Services:
1. Socket Client (initiator) for TCP or Client/Server (initiator/listener) for UDP
2. FTP Client
The TCP/UDP IP feature provides the terminal with the following benefits:
Up to four simultaneous protocol connections.
Ability to pass data via the protocol stack using AT commands (command mode). This relieves
the terminal from switching the RS232 to "binary mode" and back to "command mode".
Ability to use UDP and TCP simultaneously.
No need for protocol support from the terminal - only data sending and receiving.
Reduced memory utilization. The C24 manages the protocol stack and therefore saves
terminal memory.
Ability to open TCP connections, secured with SSL/TLS.
Ability to receive the incoming TCP connections.
Ability to accept IP connections only if the IP belongs to a defined IP white list.
TCP/IP
When establishing the TCP/IP connection the SMC MODEM can only be the "initiator". The TCP/IP
feature enables the SMC modem to be a wireless end point for a TCP/IP socket.
NOTE: The TCP protocol use the value TTL (Time to live) = 64.
Creating TCP/IP Connections
The following occurs when creating a TCP/IP connection from the SMC MODEM to the Web:
1. The SMC modem connects to the CDMA 1x network and receives an IP address (using the
AT+MIPCALL command).
2. The SMC modem opens a TCP/IP stack as one of its "sockets" (it must know the target’s IP
address and port number).
3. Once the connection is established, data is transferred freely in both directions (upload and
download).
The following occurs when creating a TCP/IP connection with another SMC modem using the
"Windows Dialer":
1. The OEM on the target side (server) uses the "Windows Dialer" application. When using this
application the TCP/IP is external to the OEM. (External TCP stack is used).
2. The target side activates the "server application" (The term "server application" means an
application that has the ability to listen on a given IP address and port number).