/***************************************************************************
 *   Copyright (C) 2010 by Michael Fischer                                 *
 *   fischer-michael@cs.yale.edu                                           *
 *                                                                         *
 *   For use in Yale course CPSC 467b, Spring 2010                         *
 ***************************************************************************/

Sample files for how to communicate using internet sockets.

This demo contains two programs.
> server port
creates a welcome socket on the local node to listen at the specified port
for an incoming internet connection.
> client host port
tries to open a connection to the given host and port.  If successful, it
sends data across to the server.  When it finishes, both programs exit.

To try them out, open two terminal windows on the same machine.  Start the
server in one, say,
> server 4444
Then in the other window, type
> client localhost 4444
The two programs should then run and print to their respective windows 
information about what is going on with the connection.

You can also try them between different machine, replacing of course
"localhost" with the host name of the machine running the server code.
However, it will fail if the server machine has a firewall that blocks the
specified port from incoming traffic.  I've tried it between two different
Zoo machines and it works there, but if you try using a server outside of
the Zoo, it might or might not work for you.

Notes on the code:

Both programs contain sleep() calls so that one can watch them run and
get some sense of the order in which things happen.  Obviously a
real-life program would not want to do this.

I have modularized both programs to some extent, trying to separate the
socket stuff from the protocol being implemented.  The modularization could
be better.  In particular, the getWelcomeInfo() function in server.c should
be made more general so that it would be useful for extracting information
from the peer socket as well as the welcome socket.

Other shortcomings of the code are:
1. Several of the primitives it uses such as gethostbyname() are now
   consider obsolete and have been replaced by newer functions.
2. The error-handling isn't very flexible.  While I've tried to detect
   errors, they are uniformly handled by printing an error message and
   aborting.

Despite these weaknesses, I think you will find this code useful in
doing problem 5b.  Please do let me know of any bugs or other problems
you encounter when using it.