http://ocotal.iarc.uaf.edu/index.php?action=history&feed=atom&title=Src-perl-Campbell%3A%3AComm 2026-04-19T20:05:18Z Revision history for this page on the wiki MediaWiki 1.34.2 http://ocotal.iarc.uaf.edu/index.php?title=Src-perl-Campbell::Comm&diff=375&oldid=prev 2007-07-06T21:27:45Z

<p></p> <p><b>New page</b></p><div>=Campbell/Comm.pm=<br /> <br /> This module becomes part of a Perl program via the '''use''' or '''require'''<br /> keywords. It provides the machinery to connect and send/receive commands<br /> to/from a remote datalogger using Perl's object-oriented programming<br /> methodology. Individual ''methods'' are provided corresponding to some/most<br /> of the ''telecommunications'' commands documented in the Campbell Scientific<br /> CR10 family manuals.<br /> <br /> Another Perl module is needed in order to interact with remote dataloggers,<br /> and that is Net::Telnet, which is included in the standard Perl distribution.<br /> This module allows automating the telnet protocol, but boils down to being<br /> able to send commands to the remote system and then wait for and handle<br /> responses -- or no response, if that's necessary.<br /> <br /> Besides the nominal TCP/IP connections, Net::Telnet is capable of supporting<br /> interfaces using a direct serial or modem connection. This usage is<br /> implemented in the (or various...) open() methods.<br /> <br /> A ''bug'' in Net::Telnet (this is my view; it may be considered a ''feature''<br /> by the authors...) requires a patch; this should be represented in the<br /> Net::Telnet version included in the above tree. Specifically, Net::Telnet<br /> goes out of its way to handle ''timeouts'' using ''wall'' time (i.e., absolute<br /> time as measured on a wall clock) rather than ''relative'' inactivity time<br /> as used in the underlying select() system function. In our case the latter<br /> form is required due to the many levels and sources of latency in the<br /> communication system.<br /> <br /> The Perl Expect module might provide a good alternative to Net::Telnet if<br /> Campbell::Comm were to be rewritten. Both provide the key functionality<br /> of being able to wait for and selectivly match on responses from the<br /> remote system.<br /> <br /> Due to the specific need to communicate with dataloggers via FreeWave<br /> radios, the Campbell::Comm module was written with this capability perhaps<br /> too implicitly. A rewrite (anticipated) should remove any code not<br /> directly concerned with the Campbell dataloggers.</div>

imported>Ken