IPL Perl Lecture Notes

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Perl Lecture Notes - Jan 11 - starting 2nd trimester

Server / Client
- The way the game works
  - Client and server applications converse over TCP/IP through "sockets" on "ports", using an agreed upon "protocol" (NTP, SOAP, FTP, HTTP, ...), many of which are layered within each other. There are CPAN modules to implement many of these pieces for you, so writing your own isn't really that tricky if you know what you want.
  - Examples here are based on IO::Socket::INET, which is a medium-level library for doing server/client communication. (lowel level is perl or system built-in socket() stuff, high level is LWP or NetServer::Generic)
  - short'n'sweet: client1, server1
  - more documentation: clientDemo, serverDemo
  - relay - putting a man in the middle to watch things
    - client1 - relay - server 1 (three terminals)
    - browser - relay - httpd
  - a silly protocol example - MTTTP
Readings
- Online:
  - perlipc - Sockets: Client/Server section
  - IO::Socket::INET, IO::Socket, IO::Handle - see here
  - various other CPAN modules :
- Dead trees:
  - at least 17.1 and 17.2 (at least) in the Sockets chapter of Cookbook
  - Camel - pg 439, Networking Clients
  - Network Programming with Perl, Lincoln Stein - there's a whole book on this stuff, available in our library. Also code available at his website, perl_networking
Assignment:
- Read (at least) chapter 1-4 in CGI Programming with Perl. This material and what follows is what we'll be looking at next. I introduced this, briefly, in my dec8 lecture. Checking back over that stuff may well be helpful. (I can almost remember that far back.)
- Your coding job this week is to write a server, or client, or (preferably) both. You can base it on the code I've shown here, or other people's code. At least one should be in Perl, but the other can be be in Java. You have two choices of what kinds of server or client to write :
  - MTTTP - the Mindless Tic Tac Toe protocol
    Write a server, client, or both to implent the MTTTP, as defined in MTTTP_protocol.txt.
  - bare bones HTTP
    Write a command line client which will fetch an page from an httpd server, something like wget or lwp-rget. You can use the relay program described in class to see what the protocl looks like. You need not implement more than the simplest dialog - unless of course you'd like to. (An example of this may be found from those in Lincoln Stein's book - see, for example, web_fetch.pl.)
    Or, write a simple httpd server. For the simplest case this is easier than you might think - the server figures out which file is requested, reads it off the disk, and sends it back to the client. If you're really having fun, you could also have it execute .cgi files and send back the output...

Have you tried Acme::Bleach yet?